Among the earliest works (if they are genuine) are the small dialogues which treat of Socratic questions and themes in a Socratic way. Of these _e. g._ the Charmides discusses temperance, the Lysis friendship, the Laches valor, the lesser Hippias knowing and wilful wrong-doing, the first Alcibiades, the moral and intellectual qualifications of a statesman, &c. The immaturity and the crudeness of these dialogues, the use of scenic means which have only an external relation to the content, the scantiness and want of independence in the content, the indirect manner of investigation which lacks a satisfactory and positive result, the formal and a.n.a.lytical treatment of the conceptions discussed-all these features indicate the early character of these minor dialogues.

The Protagoras may be taken as a proper type of the Socratic period.

Since this dialogue, though directing its whole polemic against the Sophistic philosophy, confined itself almost exclusively to the outward manifestation of this system, to its influence on its age and its method of instruction in opposition to that of Socrates, without entering into the ground and philosophical character of the doctrine itself, and, still farther, since, when it comes in a strict sense to philosophize, it confines itself, in an indirect investigation, to the Socratic conception of virtue according to its different sides (virtue as knowing, its unity and its teachableness, _cf._ -- XII. 8,)-it represents in the clearest manner the tendency, character and want of the first period of Plato's literary life.

The Gorgias, written soon after the death of Socrates, represents the third and highest stage of this period. Directed against the Sophistical identification of pleasure and virtue, of the good and of the agreeable, _i. e._ against the affirmation of an absolute moral relativity, this dialogue maintains the proof that the good, far from owing its origin only to the right of the stronger, and thus to the arbitrariness of the subject, has in itself an independent reality and objective validity, and, consequently, alone is truly useful, and thus, therefore, the measure of pleasure must follow the higher measure of the good. In this direct and positive polemic against the Sophistic doctrine of pleasure, in its tendency to a view of the good as something firm and abiding, and secure against all subjective arbitrariness, consists prominently the advance which the Gorgias makes over the Protagoras.

In the first Socratic period the Platonic philosophizing became ripe and ready for the reception of Eleatic and Pythagorean categories. To grapple by means of these categories with the higher questions of philosophy, and so to free the Socratic philosophy from its so close connection with practical life, was the task of the second period.

THE SECOND PERIOD-the dialectic or the Megaric-is marked externally, by a less prominence of form and poetic contemplation, and not unfrequently indeed, by obscurity and difficulties of style, and internally, by the attempt to give a satisfactory mediation for the Eleatic doctrine and a dialectic foundation for the doctrine of ideas.

By his exile at Megara, and his journeys to Italy, Plato became acquainted with other and opposing philosophical directions, from which he must now separate himself in order to elevate the Socratic doctrine to its true significance. It was now that he first learned to know the philosophic theories of the earlier sages, for whose study the necessary means could not at that period, so wanting in literary publicity, be found at Athens. By his separation from these varying standpoints, as his older fellow pupils had already striven to do, he attempted striding over the narrow limits of ethical philosophizing, to reach the final ground of knowing, and to carry out the art of forming conceptions as brought forward by Socrates, to a science of conceptions, _i. e._ to the doctrine of ideas. That all human acting depends upon knowing, and that all thinking depends upon the conception, were results to which Plato might already have attained through the scientific generalization of the Socratic doctrine itself, but now to bring this Socratic wisdom within the circle of speculative thinking, to establish dialectically that the conception in its simple unity is that which abides in the change of phenomena, to disclose the fundamental principles of knowledge which had been evaded by Socrates, to grasp the scientific theories of the opposers direct in their scientific grounds, and follow them out in all their ramifications,-this is the problem which the Megaric family of dialogues attempts to solve.

The Theataetus stands at the head of this group. This is chiefly directed against the Protagorean theory of knowledge, against the identification of the thinking and the sensible perception, or against the claim of an objective relativity of all knowledge. As the Gorgias before it had sought to establish the independent being of the ethical, so does the Theataetus ascending from the ethical to the theoretical, endeavor to prove an independent being and objective reality for the logical conceptions which lie at the ground of all representation and thinking, in a word, to prove the objectivity of truth, the fact that there lies a province of thought immanent in the thinking and independent of the perceptions of the senses. These conceptions, whose objective reality is thus affirmed, are those of a species, likeness and unlikeness, sameness and difference, &c.

The Theataetus is followed by the trilogy of the Sophist, the Statesman, and the Philosopher, which completes the Megaric group of dialogues. The first of these dialogues examines the conception of appearance, that is of the not-being, the last (for which the Parmenides may be taken) the conception of being. Both dialogues are especially directed to the Eleatic doctrine. After Plato had recognized the conception in its simple unity as that which abides in the change of phenomena, his attention was naturally turned towards the Eleatics, who in an opposite way had attained the similar result that in unity consists all true substantiality, and to multiplicity as such no true being belongs. In order more easily on the one side to carry out this fundamental thought of the Eleatic to its legitimate result, in which the Megarians had already preceded him, he was obliged to give a metaphysical substance to his abstract conceptions of species, _i. e._ ideas. But on the other side, he could not agree with the inflexibility and exclusiveness of the Eleatic unity, unless he would wholly sacrifice the multiplicity of things; he was rather obliged to attempt to show by a dialectic development of the Eleatic principle that the one must be at the same time a totality, organically connected, and embracing multiplicity in itself. This double relation to the Eleatic principle is carried out by the Sophist and the Parmenides; by the former polemically against the Eleatic doctrine, in that it proves the being of the appearance or the not-being, and by the latter pacifically, in that it a.n.a.lyzes the Eleatic one by its own logical consequences into many. The inner progress of the doctrine of Ideas in the Megaric group of dialogues is therefore this, viz., that the Theataetus, in opposition to the Herac.l.i.tico-Protagorean theory of the absolute becoming, affirms the objective and independent reality of ideas, and the Sophist shows their reciprocal relation and combining qualities, while the Parmenides in fine exhibits their whole dialectic completeness with their relation to the phenomenal world.

THE THIRD PERIOD begins with the return of the philosopher to his native city. It unites the completeness of form belonging to the first with the profounder characteristical content belonging to the second. The memories of his youthful years seem at this time to have risen anew before the soul of Plato, and to have imparted again to his literary activity the long lost freshness and fulness of that period, while at the same time his abode in foreign lands, and especially his acquaintance with the Pythagorean philosophy, had greatly enriched his mind with a store of images and ideals. This reviving of old memories is seen in the fact that the writings of this group return with fondness to the personality of Socrates, and represent in a certain degree the whole philosophy of Plato as the exaltation of the doctrine and the ideal embodiment of the historical character of his early master. In opposition to both of the first two periods, the third is marked externally by an excess of the mythical form connected with the growing influence of Pythagoreanism in this period, and internally by the application of the doctrine of ideas to the concrete spheres of psychology, ethics and natural science. That ideas possess objective reality, and are the foundation of all essentiality and truth, while the phenomena of the sensible world are only copies of these, was a theory whose vindication was no longer attempted, but which was presupposed as already proved, and as forming a dialectical basis for the pursuit of the different branches of science. With this was connected a tendency to unite the hitherto separate branches of science into a systematic whole, as well as to mould together the previous philosophical directions, and show the inner application of the Socratic philosophy for ethics, of the Eleatic for dialectics, and the Pythagorean for physics.

Upon this standpoint, the Phaedrus, Plato's inaugural to his labors in the Academy, together with the Symposium, which is closely connected with it, attempts to subject the rhetorical theory and practice of their time to a thorough criticism, in order to show in opposition to this theory and practice, that the fixedness and stability of a true scientific principle could only be attained by grounding every thing on the idea. On the same standpoint the Phaedon attempts to prove the immortality of the soul from the doctrine of ideas; the Philebus to bring out the conception of pleasure and of the highest good; the Republic to develop the essence of the state, and the Timaeus that of nature.

Having thus sketched the inner development of the Platonic philosophy, we now turn to a systematic statement of its principles.

III.-CLa.s.sIFICATION OF THE PLATONIC SYSTEM.-The philosophy of Plato, as left by himself, is without a systematic statement, and has no comprehensive principle of cla.s.sification. He has given us only the history of his thinking, the statement of his philosophical development; we are therefore limited in reference to his cla.s.sification of philosophy to simple intimations. Accordingly, some have divided the Platonic system into theoretical and practical science, and others into a philosophy of the good, the beautiful and the true. Another cla.s.sification, which has some support in old records, is more correct.

Some of the ancients say that Plato was the first to unite in one whole the scattered philosophical elements of the earlier sages, and so to obtain for philosophy the three parts, logic, physics, and ethics. The more accurate statement is given by _s.e.xtus Empiricus_, that Plato has laid the foundation for this threefold division of philosophy, but that it was first expressly recognized and affirmed by his scholars, Xenocrates and Aristotle. The Platonic system may, however, without difficulty, be divided into these three parts. True, there are many dialogues which mingle together in different proportions the logical, the ethical, and the physical element, and though even where Plato treats of some special discipline, the three are suffered constantly to interpenetrate each other, still there are some dialogues in which this fundamental scheme can be clearly recognized. It cannot be mistaken that the Timaeus has predominantly a physical, and the Republic as decidedly an ethical element, and if the dialectic is expressly represented in no separate dialogue, yet does the whole Megaric group pursue the common end of bringing out the conception of science and its true object, being, and is, therefore, in its content decidedly dialectical. Plato must have been led to this threefold division by even the earlier development of philosophy, and though Xenocrates does not clearly see it, yet since Aristotle presupposes it as universally admitted, we need not scruple to make it the basis on which to represent the Platonic system.

The order which these different parts should take, Plato himself has not declared. Manifestly, however, dialectics should have the first place as the ground of all philosophy, since Plato uniformly directs that every philosophical investigation should begin with accurately determining the _idea_ (_Phaed._ p. 99. Phaedr. p. 237), while he subsequently examines all the concrete spheres of science on the standpoint of the doctrine of ideas. The relative position of the other two parts is not so clear.

Since, however, the physics culminates in the ethics, and the ethics, on the other hand, has for its basis physical investigations into the ensouling power in nature, we may a.s.sign to physics the former place of the two.

The mathematical sciences Plato has expressly excluded from philosophy.

He considers them as helps to philosophical thinking (_Rep._ VII. 526), as necessary steps of knowledge, without which no one can come to philosophy (_Ib._ VI. 510); but mathematics with him is not philosophy, for it a.s.sumes its principles or axioms, without at all accounting for them, as though they were manifest to all, a procedure which is not permitted to pure science; it also serves itself for its demonstrations, with ill.u.s.trative figures, although it does not treat of these, but of that which they represent to the understanding (_Ib._). Plato thus places mathematics midway between a correct opinion and science, clearer than the one, but more obscure than the other. (_Ib._ VII. 533.)

IV. THE PLATONIC DIALECTICS. 1. CONCEPTION OF DIALECTICS.-The conception of dialectics or of logic, is used by the ancients for the most part in a very wide sense, while Plato employs it in repeated instances interchangeably with philosophy, though on the other hand he treats it also as a separate branch of philosophy. He divides it from physics as the science of the eternal and unchangeable from the science of the changeable, which never is, but is only ever becoming; he distinguishes also between it and ethics, so far as the latter treats of the good not absolutely, but in its concrete exhibition in morals and in the state; so that dialectics may be termed philosophy in a higher sense, while physics and ethics follow it as two less exact sciences, or as a not yet perfected philosophy. Plato himself defines dialectics, according to the ordinary signification of the word, as the art of developing knowledge by way of dialogue in questions and answers. (_Rep._ VII. 534). But since the art of communicating correctly in dialogue is according to Plato, at the same time the art of thinking correctly, and as thus thinking and speaking could not be separated by the ancients, but every process of thought was a living dialogue, so Plato would more accurately define dialectics as the science which brings speech to a correct issue, and which combines or separates the species, _i. e._ the conceptions of things correctly with one another. (_Soph._ p. 253. _Phaedr._ p. 266).

Dialectics with him has two divisions, to know what can and what cannot be connected, and to know how division or combination can be. But as with Plato these conceptions of species or ideas are the only actual and true existence, so have we, in entire conformity with this, a third definition of dialectics (_Philebus_ p. 57), as the science of being, the science of that which is true and unchangeable, the science of all other sciences. We may therefore briefly characterize it as the science of absolute being or of ideas.

2. WHAT IS SCIENCE? (1.) _As opposed to sensation and the sensuous representation._-The Theataetus is devoted to the discussion of this question in opposition to the Protagorean sensualism. That all knowledge consists in perception, and that the two are one and the same thing, was the Protagorean proposition. From this it followed, as Protagoras himself had inferred, that things are, as they appear to me, that the perception or sensation is infallible. But since perception and sensation are infinitely diversified with different individuals, and even greatly vary in the same individual, it follows farther, that there are no objective determinations and predicates, that we can never affirm what a thing is in itself, that all conceptions, great, small, light, heavy, to increase, to diminish, &c., have only a relative significance, and consequently, also, the conceptions of species, as combinations of the changeful many, are wholly wanting in constancy and stability. In opposition to this Protagorean thesis, Plato urges the following objections and contradictions. _First._ The Protagorean doctrine leads to the most startling consequences. If being and appearance, knowledge and perception are one and the same thing, then is the irrational brute, which is capable of perception, as fully ent.i.tled to be called the measure of all things, as man, and if the representation is infallible, as the expression of my subjective character at a given time, then need there be no more instruction, no more scientific conclusion, no more strife, and no more refutation. _Second._ The Protagorean doctrine is a logical contradiction; for according to it Protagoras must yield the question to every one who disputes with him, since, as he himself affirms, no one is incorrect, but every one judges only according to truth; the pretended truth of Protagoras is therefore true for no man, not even for himself. _Third._ Protagoras destroys the knowledge of future events. That which I may regard as profitable may not therefore certainly prove itself as such in the result. To determine that which is really profitable implies a calculation of the future, but since the ability of men to form such a calculation is very diverse, it follows from this that not man as such, but only the wise man can be the measure of things. _Fourth._ The theory of Protagoras destroys perception.

Perception, according to him, rests upon a distinction of the perceived object and the perceiving subject, and is the common product of the two.

But in his view the objects are in such an uninterrupted flow, that they can neither become fixed in seeing nor in hearing. This condition of constant change renders all knowledge from sense, and hence (the ident.i.ty of the two being a.s.sumed), all knowledge impossible. _Fifth._ Protagoras overlooks the apriori element in knowledge. It is seen in an a.n.a.lysis of the sense-perception itself, that all knowledge cannot be traced to the activity of the senses, but that there must also be presupposed besides these, intellectual functions, and hence an independent province of supersensible knowledge. We see with the eyes, and hear with the ears, but to group together the perceptions attained through these different organs, and to hold them fast in the unity of self-consciousness, is beyond the power of the activity of the senses.

Again, we compare the different sense-perceptions with one another, a function which cannot belong to the senses, since each sense can only furnish its own distinctive perception. Still farther, we bring forward determinations respecting the perceptions which we manifestly cannot owe to the senses, in that we predicate of these perceptions, being and not-being, likeness and unlikeness, &c. These determinations, to which also belong the beautiful and the odious, good and evil, const.i.tute a peculiar province of knowledge, which the soul, independently of every sense-perception, brings forward through its own independent activity.

The ethical element of this Plato exhibits in his attack upon sensualism, and also in other dialogues. He maintains (_in the Sophist_), that men holding such opinions must be improved before they can be instructed, and that when made morally better, they will readily recognize the truth of the soul and its moral and rational capacities, and affirm that these are real things, though objects of neither sight nor of feeling.

(2.) _The Relation of Knowing to Opinion._-Opinion is just as little identical with knowing as is the sense-perception. An incorrect opinion is certainly different from knowing, and a correct one is not the same, for it can be engendered by the art of speech without therefore attaining the validity of true knowledge. The correct opinion, so far as it is true in matter though imperfect in form, stands rather midway between knowing and not-knowing, and partic.i.p.ates in both.

(3.) _The Relation of Science to Thinking._-In opposition to the Protagorean sensualism, we have already referred to an energy of the soul independent of the sensuous perception and sensation, competent in itself to examine the universal, and grasp true being in thought. There is, therefore, a double source of knowledge, sensation and rational thinking. Sensation refers to that which is conceived in the constant becoming and perpetual change, to the pure momentary, which is in an incessant transition from the was, through the now, into the shall be (_Parm._ p. 152); it is, therefore, the source of dim, impure, and uncertain knowledge; thinking on the other hand refers to the abiding, which neither becomes nor departs, but remains ever the same. (_Tim._ p.

51.) Existence, says the Timaeus (p. 27) is of two kinds, "that which ever is but has no becoming, and that which ever becomes but never is.

The one kind, which is always in the same state, is comprehended through reflection by the reason, the other, which becomes and departs, but never properly is, may be apprehended by the sensuous perception without the reason." True science, therefore, flows alone from that pure and thoroughly internal activity of the soul which is free from all corporeal qualities and every sensuous disturbance. (_Phaed._ p. 65.) In this state the soul looks upon things purely as they are (_Phaed._ p. 66) in their eternal being and their unchangeable condition. Hence the true state of the philosopher is announced in the Phaedon (p. 64) to be a willingness to die, a longing to fly from the body, as from a hinderance to true knowledge, and become pure spirit. According to all this, science is the thinking of true being or of ideas; the means to discover and to know these ideas, or the organ for their apprehension is the dialectic, as the art of separating and combining conceptions; the true objects of dialectics are ideas.

3. THE DOCTRINE OF IDEAS IN ITS GENESIS.-The Platonic doctrine of ideas is the common product of the Socratic method of forming conceptions, the Herac.l.i.tic doctrine of absolute becoming, and the Eleatic doctrine of absolute being. To the first of these Plato owes the idea of a knowing through conceptions, to the second the recognition of the becoming in the field of the sensuous, to the third the position of a field of absolute reality. Elsewhere (_in the Philebus_) Plato connects the doctrine of ideas with the Pythagorean thought that every thing may be formed from unity and multiplicity, from the limit and the unlimited.

The aim of the Theataetus, the Sophist, and the Parmenides is to refute the principles of the Eleatics and Herac.l.i.tics: this refutation is effected in the Theataetus by combating directly the principle of an absolute becoming, in the Sophist by combating directly the principle of abstract being, and in the Parmenides by taking up the Eleatic one and showing its true relations. We have already spoken of the Theataetus; we will now look for the development of the doctrine of ideas in the Sophist and Parmenides.

The ostensible end of the former of these dialogues is to show that the Sophist is really but a caricature of the philosopher, but its true end is to fix the reality of the appearance, _i. e._ of the not-being, and to discuss speculatively the relation of being and not-being. The doctrine of the Eleatics ended with the rejection of all sensuous knowledge, declaring that what we receive as the perception of a multiplicity of things or of a becoming is only an appearance. In this the contradiction was clear, the not-being was absolutely denied, and yet its existence was admitted in the notion of men. Plato at once draws attention to this contradiction, showing that a delusive opinion, which gives rise to a false image or representation, is not possible, since the whole theory rests upon the a.s.sumption that the false, the not-true, _i. e._ not-being cannot even be thought. This, Plato continues, is the great difficulty in thinking of not-being, that both he who denies and he who affirms its reality is driven to contradict himself. For though it is inexpressible and inconceivable either as one or as many, still, when speaking of it, we must attribute to it both being and multiplicity. If we admit that there is such a thing as a false opinion, we a.s.sume in this very fact the notion of not-being, for only that opinion can be said to be false which supposes either the not-being to be, or makes that, which is not, to be. In short, if there actually exists a false notion, so does there actually and truly exist a not-being. After Plato had thus fixed the reality of not-being, he discusses the relation of being and not-being, _i. e._ the relation of conceptions generally in their combinations and differences. If not-being has no less reality than being, and being no more than not-being, if, therefore, _e. g._ the not-great is as truly real as the great, then every conception may be apprehended according to its opposite sides as being and not-being at the same time: it is a being in reference to itself, as something identical with itself, but it is not-being in reference to every one of the numberless other conceptions which can be referred to it, and with which, on account of its difference from them, it can have nothing in common. The conception of the same ta?t?? and the different ??te??? represent the general form of an ant.i.thesis. These are the universal formulae of combination for all conceptions. This reciprocal relation of conceptions as at the same time being and not-being, by virtue of which they can be arranged among themselves, forms now the basis for the art of dialectics, which has to judge what conceptions can and what cannot be joined together. Plato ill.u.s.trates here by taking the conceptions of being, motion (becoming), and rest (existence), and showing what are the results of the combinations of these ideas. The conceptions of motion and rest cannot well be joined together, though both of them may be joined with that of being, since both are; the conception of rest is therefore in reference to itself a being, but in reference to the conception of motion a not-being or different. Thus the Platonic doctrine of ideas, after having in the Theataetus attained its general foundation in fixing the objective reality of conceptions, becomes now still farther developed in the Sophist to a doctrine of the agreement and disagreement of conceptions. The category which conditions these reciprocal relations is that of not-being or difference. This fundamental thought of the Sophist, that being is not without not-being and not-being is not without being, may be expressed in modern phraseology thus: negation is not not-being but determinateness, and on the other hand all determinateness and concreteness of conceptions, or every thing affirmative can be only through negation; in other words the conception of contradiction is the soul of a philosophical method.

The doctrine of ideas appears in the Parmenides as the positive consequence and progressive development of the Eleatic principle. Indeed in this dialogue, in that Plato makes Parmenides the chief speaker, he seems willing to allow that his doctrine is in substance that of the Eleatic sage. True, the fundamental thought of the dialogue-that the one is not conceivable in its complete singleness without the many, nor the many without the one, that each necessarily presupposes and reciprocally conditions the other-stands in the most direct contradiction to Eleaticism. Yet Parmenides himself, by dividing his poem into two parts, and treating in the first of the one and in the second of the many, postulates an inner mediation between these two externally so disjointed parts of his philosophy, and in this respect the Platonic theory of ideas might give itself out as the farther elimination, and the true sense of the Parmenidean philosophizing. This dialectical mediation between the one and the not-one or the many Plato now attempts in four antinomies, which have ostensibly only a negative result in so far as they show that contradictions arise both whether the one be adopted or rejected. The positive sense of these antinomies, though it can be gained only through inferences which Plato himself does not expressly utter, but leaves to be drawn by the reader-is as follows. The first antinomy shows that the one is inconceivable as such since it is only apprehended in its abstract opposition to the many; the second, that in this case also the reality of the many is inconceivable; the third, that the one or the idea cannot be conceived as not-being, since there can be neither conception nor predicate of the absolute not-being, and since, if not-being is excluded from all fellowship with being, all becoming and departing, all similarity and difference, every representation and explanation concerning it must also be denied; and lastly, the fourth affirms that the not-one or the many cannot be conceived without the one or the idea. What now is Plato's aim in this discussion of the dialectic relations between the conceptions of the one and the many? Would he use the conception of the one only as an example to explain his dialectic method with conceptions, or is the discussion of this conception itself the very object before him? Manifestly the latter, or the dialogue ends without result and without any inner connection of its two parts. But how came Plato to make such a special investigation of this conception of the one? If we bear in mind that the Eleatics had already perceived the ant.i.thesis of the actual and the phenomenal world in the ant.i.thesis of the one and the many, and that Plato himself had also regarded his ideas as the unity of the manifold, as the one and the same in the many-since he repeatedly uses "idea" and "the one" in the same sense, and places (_Rep._ VII. 537) dialectics in the same rank with the faculty of bringing many to unity-then is it clear that the one which is made an object of investigation in the Parmenides is the idea in its general sense, _i. e._ in its logical form, and that Plato consequently in the dialectic of the one and the many would represent the dialectic of the idea and the phenomenal world, or in other words would dialectically determine and establish the correct view of the idea as the unity in the manifoldness of the phenomenal. In that it is shown in the Parmenides, on the one side, that the many cannot be conceived without the one, and on the other side, that the one must be something which embraces in itself manifoldness, so have we the ready inference on the one side, that the phenomenal world, or the many, has a true being only in so far as it has the one or the conception within it, and on the other side, that since the conception is not an abstract one but manifoldness in unity, it must actually have manifoldness in unity in order to be able to be in the phenomenal world. The indirect result of the Parmenides is that matter as the infinitely divisible and undetermined ma.s.s has no actuality, but is in relation to the ideal world a not-being, and though the ideas as the true being gain their appearance in it, yet the idea itself is all that is actual in the appearance or phenomenon; the phenomenal world derives its whole existence from the ideal world which appears in it, and has a being only so far as it has a conception or idea for its content.

4. POSITIVE EXPOSITION OF THE DOCTRINE OF IDEAS.-Ideas may be defined according to the different sides of their historical connection, as the common in the manifold, the universal in the particular, the one in the many, or the constant and abiding in the changing. Subjectively they are principles of knowing which cannot be derived from experience they are the intuitively certain and innate regulators of our knowledge.

Objectively they are the immutable principles of being and of the phenomenal world, incorporeal and simple unities which have no relation to s.p.a.ce, and which may be predicated of every independent thing. The doctrine of ideas grew originally out of the desire to give a definite conception to the inner essence of things, and make the real world conceivable as a harmoniously connected intellectual world. This desire of scientific knowledge Aristotle cites expressly as the motive to the Platonic doctrine of ideas. "Plato," he says (_Metaph._ XIII. 4), "came to the doctrine of ideas because he was convinced of the truth of the Herac.l.i.tic view which regarded the sensible world as a ceaseless flowing and changing. His conclusion from this was, that if there be a science of any thing there must be, besides the sensible, other substances which have a permanence, for there can be no science of the fleeting." It is, therefore, the idea of science which demands the reality of ideas, a demand which cannot be granted unless an idea or conception is also the ground of all being. This is the case with Plato. According to him there can be neither a true knowing nor a true being without ideas and conceptions which have an independent reality.

What now does Plato mean by idea? From what has already been said it is clear that he means something more than ideal conceptions of the beautiful and the good. An idea is found, as the name itself (e?d??) indicates, wherever a universal conception of a species or kind is found. Hence Plato speaks of the idea of a bed, table, strength, health, voice, color, ideas of simple relations and properties, ideas of mathematical figures, and even ideas of not-being, and of that, which in its essence only contradicts the idea, baseness and vice. In a word, we may put an idea wherever many things may be characterized by a common name (_Rep._ X. 596): or as Aristotle expresses it (_Met._ XII. 3).

Plato places an idea to every cla.s.s of being. In this sense Plato himself speaks in the beginning of the Parmenides. Parmenides asks the young Socrates what he calls ideas. Socrates answers by naming unconditionally the moral ideas, the ideas of the true, the beautiful, the good, and then after a little delay he mentions some physical ones, as the ideas of man, of fire, of water; he will not allow ideas to be predicated of that which is only a formless ma.s.s, or which is a part of something else, as hair, mud and clay, but in this he is answered by Parmenides, that if he would be fully imbued with philosophy, he must not consider such things as these to be wholly despicable, but should look upon them as truly though remotely partic.i.p.ating in the idea. Here at least the claim is a.s.serted that no province of being is excluded from the idea, that even that which appears most accidental and irrational is yet a part of rational knowledge, in fact that every thing existing may be brought within a rational conception.

5. THE RELATION OF IDEAS TO THE PHENOMENAL WORLD. a.n.a.logous to the different definitions of idea are the different names which Plato gives to the sensible and phenomenal world. He calls it the many, the divisible, the unbounded, the undetermined and measureless, the becoming, the relative, great and small, not-being. The relation now in which these two worlds of sense and of ideas stand to each other is a question which Plato has answered neither fully nor consistently with himself. His most common way is to characterize the relation of things to conceptions as a partic.i.p.ant, or to call things the copies and adumbrations, while ideas are the archetypes. Yet this is so indefinite that Aristotle properly says that to talk in this way is only to use poetical metaphors. The great difficulty of the doctrine of ideas is not solved but only increased by these figurative representations. The difficulty lies in the contradiction which grows out of the fact that while Plato admits the reality of the becoming and of the province of the becoming, he still affirms that ideas which are substances ever at rest and ever the same are the only actual. Now in this Plato is formally consistent with himself, while he characterizes the _materiel_ of matter not as a positive substratum but as not-being, and guards himself with the express affirmation that he does not consider the sensible as being, but only as something similar to being. (_Rep._ X.

597.) The position laid down in the Parmenides is also consistent with this, that a perfect philosophy should look upon the idea as the cognizable in the phenomenal world, and should follow it out in the smallest particulars until every part of being should be known and all dualism removed. In fine, Plato in many of his expressions seems to regard the world of sensation only as a subjective appearance, as a product of the subjective notion, as the result of a confused way of representing ideas. In this sense the phenomena are entirely dependent on ideas; they are nothing but the ideas themselves in the form of not being; the phenomenal world derives its whole existence from the ideal world which appears in it. But yet when Plato calls the sensible a mingling of the same with the different or the not-being (_Tim._ p. 35), when he characterizes the ideas as vowels which go through every thing like a chain (_Soph._ p. 253), when he himself conceives the possibility that matter might offer opposition to the formative energy of ideas (_Tim._ p. 56), when he speaks of an evil soul of the world (_de Leg._ X. 896), and gives intimations of the presence in the world of a principle in nature hostile to G.o.d (_Polit._ p. 268), when he in the Phaedon treats of the relation between body and soul as one wholly discordant and malignant,-in all this there is evidence enough, even after allowing for the mythical form of the Timaeus, and the rhetorical composition which prevails in the Phaedon, to substantiate the contradiction mentioned above. This is most clear in the Timaeus. Plato in this dialogue makes the sensible world to be formed by a Creator after the pattern of an idea, but in this he lays down as a condition that this Demi-urge or Creator should find at hand a something which should be apt to receive and exhibit this ideal image. This something Plato compares to the matter which is fashioned by the artisan (whence the later name _hyle_). He characterizes it as wholly undetermined and formless, but possessing in itself an apt.i.tude for every variety of forms, an invisible and shapeless thing, a something which it is difficult to characterize, and which Plato even does not seem inclined very closely to describe. In this the actuality of matter is denied; while Plato makes it equivalent to s.p.a.ce it is only the place, the negative condition of the sensible while it possesses a being only as it receives in itself the ideal form. Still matter remains the objective and phenomenal form of the idea: the visible world arises only through the mingling of ideas with this substratum, and if matter be metaphysically expressed as "the different," then does it follow with logical necessity in a dialectical discussion that it is just as truly being as not-being. Plato does not conceal from himself this difficulty, and therefore attempts to represent with comparisons and images this presupposition of a _hyle_ which he finds it as impossible to do without as to express in a conceivable form. If he would do without it he must rise to the conception of an absolute creation, or consider matter as an ultimate emanation from the absolute spirit, or else explain it as appearance only. Thus the Platonic system is only a fruitless struggle against dualism.

6. THE IDEA OF THE GOOD AND THE DEITY. If the true and the real is exhibited in general conceptions which are so related to each other that every higher conception embraces and combines under it several lower, so that any one starting from a single idea may eventually discover all (_Meno._ p. 81), then must the sum of ideas form a connected organism and succession in which the lower idea appears as a stepping-stone and presupposition to a higher. This succession must have its end in an idea which needs no higher idea or presupposition to sustain it. This highest idea, the ultimate limit of all knowledge, and itself the independent ground of all other ideas, Plato calls the idea of the good, _i. e._ not of the moral but of the metaphysical good. (_Rep._ VII. 517.)

What this good is in itself, Plato undertakes to show only in images.

"In the same manner as the sun," he says in the Republic (VI. 506), "is the cause of sight, and the cause not merely that objects are visible but also that they grow and are produced, so the good is of such power and beauty, that it is not merely the cause of science to the soul, but is also the cause of being and reality to whatever is the object of science, and as the sun is not itself sight or the object of sight but presides over both, so the good is not science and truth but is superior to both, they being not the good itself but of a goodly nature." The good has unconditioned worth, and gives to every other thing all the value it possesses. The idea of the good excludes all presupposition. It is the ultimate ground at the same time of knowing and of being, of the perceiver and the perceived, of the subjective and the objective, of the ideal and the real, though exalted itself above such a division. (_Rep._ VI. 508-517.) Plato, however, has not attempted a derivation of the remaining ideas from the idea of the good; his course here is wholly an empirical one; a certain cla.s.s of objects are taken, and having referred these to their common essence this is given out as their idea. He has treated the individual conceptions so independently, and has made each one so complete in itself, that it is impossible to find a proper division or establish an immanent continuation of one into another.

It is difficult to say precisely what relation this idea of the good bore to the Deity in the Platonic view. Taking every thing together it seems clear that Plato regarded the two as identical, but whether he conceived this highest cause to be a personal being or not is a question which hardly admits of a definite answer. The logical result of his system would exclude the personality of G.o.d. If only the universal (the idea) is the true being, then can the only absolute idea, the Deity, be only the absolute universal; but that Plato was himself conscious of this logical conclusion we can hardly affirm, any more than we can say on the other hand that he was clearly a theist. For whenever in a mythical or popular statement he speaks of innumerable G.o.ds, this only indicates that he is speaking in the language of the popular religion, and when he speaks in an accurate philosophical sense, he only makes the relation of the personal deity with the idea a very uncertain one. Most probable, therefore, is it that this whole question concerning the personality of G.o.d was not yet definitely before him, that he took up the religious idea of G.o.d and defended it in ethical interest against the anthropomorphism of the mythic poets, that he sought to establish it by arguments drawn from the evidences of design in nature, and the universal prevalence of a belief in a G.o.d, while as a philosopher he made no use of it.

V. THE PLATONIC PHYSICS. 1. NATURE.-The connection between the Physics and the Dialectics of Plato lies princ.i.p.ally in two points-the conception of becoming, which forms the chief property of nature, and that of real being, which is at once the all sufficient and good, and the true end of all becoming. Because nature belongs to the province of irrational sensation we cannot look for the same accuracy in the treatment of it, as is furnished in dialectics. Plato therefore applied himself with much less zest to physical investigations than to those of an ethical or dialectical character, and indeed only attended to them in his later years. Only in one dialogue, the Timaeus, do we find any extended evolution of physical doctrines, and even here Plato seems to have gone to his work with much less independence than his wont, this dialogue being more strongly tinctured with Pythagoreanism than any other of his writings. The difficulty of the Timaeus is increased by the mythical form on which the old commentators themselves have stumbled. If we take the first impression that it gives us, we have, before the creation of the world, a Creator as a moving and a reflecting principle, with on the one side the ideal world existing immovable as the eternal archetype, and on the other side, a chaotic, formless, irregular, fluctuating ma.s.s, which holds in itself the germ of the material world, but has no determined character nor substance. With these two elements the Creator now blends the world-soul which he distributes according to the relation of numbers, and sets it in definite and harmonious motion.

In this way the material world, which has become actual through the arrangement of the chaotic ma.s.s into the four elements, finds its external frame, and the process thus begun is completed in its external structure by the formation of the organic world.

It is difficult to separate the mythical and the philosophical elements in this cosmogony of the Timaeus, especially difficult to determine how far the historical construction, which gives a succession in time to the acts of creation, is only a formal one, and also how far the affirmation that matter is absolutely a not-being can be harmonized with the general tenor of Plato's statements. The significance of the world-soul is clearer. Since the soul in the Platonic system is the mean between spirit and body, and as in the same way mathematical relations, in their most universal expression as numbers, are the mean between mere sensuous existence and the pure idea (between the one and the many as Plato expresses it), it would seem clear that the world-soul, construed according to the relation of numbers, must express the relation of the world of ideas to that of sense, in other words, that it denotes the sensible world as a thought represented in the form of material existence. The Platonic view of nature, in opposition to the mechanical attempts to explain it of the earlier philosophers, is entirely teleological, and based upon the conception of the good, or, on the moral idea. Plato conceives the world as the image of the good, as the work of the divine munificence. As it is the image of the perfect it is therefore only one, corresponding to the idea of the single all-embracing substance, for an infinite number of worlds is not to be conceived as actual. For the same reason the world is spherical, after the most perfect and uniform structure, which embraces in itself all other forms; its movement is in a circle, because this, by returning into itself, is most like the movement of reason. The particular points of the Timaeus, the derivation of the four elements, the separation of the seven planets according to the musical scale, the opinion that the stars were immortal and heavenly substances, the affirmation that the earth holds an abiding position in the middle of the world, a view which subsequently became elaborated to the Ptolemaic system, the reference of all material figures to the triangle as the simplest plane figure, the division of inanimate nature, according to the four elements, into creatures of earth, water, and air, his discussions respecting organic nature, and especially respecting the construction of the human body-all these we need here only mention. Their philosophical worth consists not so much in their material content, but rather in their fundamental idea, that the world should be conceived as the image and the work of reason, as an organism of order, harmony, and beauty, as the good actualizing itself.

2. THE SOUL.-The doctrine of the soul, considering it simply as the basis of a moral action, and leaving out of view all questions of concrete ethics, forms a const.i.tuent element in the Platonic physics.

Since the soul is united to the body, it partic.i.p.ates in the motions and changes of the body, and is, in this respect, related to the perishable.

But in so far as it partic.i.p.ates in the knowledge of the eternal, _i.

e._ in so far as it knows ideas, does there live within it a divine principle-reason. Accordingly, Plato distinguishes two components of the soul-the divine and the mortal, the rational and the irrational. These two are united by an intermediate link, which Plato calls ???? or spirit, and which, though allied to reason is not reason itself, since it is often exhibited in children and also in brutes, and since even men are often carried away by it without reflection. This threefoldness, here exhibited psychologically, is found, in different applications, through all the last general period of Plato's literary life. Based upon the anthropological triplicate of reason, soul and body, it corresponds also to the division of theoretical knowledge into science (or thinking), correct opinions (or sense-perception), and ignorance, to the triple ladder of eroticism in the Symposium and the mythological representation connected with this of Poros, Eros, and Penia; to the metaphysical triplicate of the ideal world, mathematical relations and the sensible world; and furnishes ground for deriving the ethical division of virtue and the political division of ranks.

So far as the soul is a mean between the spiritual and corporeal, may we connect the Phaedon's proofs of its immortality with the psychological view now before us. The common thought of these arguments is that the soul, in its capacity for thinking, partic.i.p.ates in the reason, and being thus of an opposite nature to, and uncontrolled by the corporeal, it may have an independent existence. The arguments are wholly a.n.a.lytical, and possess no valid and universal proof; they proceed entirely upon a _pet.i.tio principii_, they are derived partly from mythical philosophemes, and manifest not only an obscure conception of the soul, but of its relations to the body and the reason, and, so far as the relation of the soul to the ideal world is in view, they furnish in the best case only some proof for the immortality of him who has raised his soul to a pure spirit, _i. e._ the immortality of the philosopher. Plato was not himself deceived as to the theoretical insufficiency of his arguments. Their number would show this, and, besides, he expressly calls them proofs which amount to only human probability, and furnish practical postulates alone. With this view he introduces at the close of his arguments the myth of the lower world, and the state of departed souls, in order, by complying with the religious notions, and traditions of his countrymen, to gain a positive support for belief in the soul's immortality. Elsewhere Plato also speaks of the lower world, and of the future rewards and punishments of the good and the evil, in accordance with the popular notions, as though he saw the elements of a divine revelation therein; he tells of purifying punishment in Hades, a.n.a.logous to a purgatory; he avails himself of the common notion to affirm that shades still subject to the corporeal principle will hover after death over their graves, seeking to recover their lifeless bodies, and at times he dilates upon the migration of the soul to various human and brute forms. On the whole, we find in Plato's proofs of immortality, as in his psychology generally, that dualism, which here expresses itself as hatred to the corporeal, and is connected with the tendency to seek the ultimate ground of evil in the nature of the "different" and the sensible world.

VI. THE PLATONIC ETHICS.-The ground idea of the good, which in physics served only as an inventive conception, finds now, in the ethics, its true exhibition. Plato has developed it prominently according to three sides, as good, as individual virtue, and as ethical world in the state.

The conception of duty remains in the background with him as with the older philosophers.

1. GOOD AND PLEASURE.-That the highest good can be nothing other than the idea of the good itself, has already been shown in the dialectics, where this idea was suffered to appear as the ultimate end of all our striving. But since the dialectics represent the supreme good as unattainable by human reason, and only cognizable in its different modes of manifestation, we can, therefore, only follow these different manifestations of the highest good, which represent not the good itself, but the good in becoming, where it appears as science, truth, beauty, virtue, &c. We are thus not required to be equal to G.o.d, but only like him (_Theaet._) It is this point of view which lies at the basis of the graduated table of good, given in the Philebus.

In seeking the highest good, the conception of pleasure must be investigated. The Platonic standpoint here is the attempt to strike a balance between Hedonism, (the Cyrenian theory that pleasure is the highest good, _cf._ -- XIII. 3), and Cynicism. While he will not admit with Aristippus that pleasure is the true good, neither will he find it as the Cynics maintain, simply in the negation of its contrary, pain, and thus deny that it belongs to the good things of human life. He finds his refutation of Hedonism in the indeterminateness and relativity of all pleasure, since that which at one time may seem as pleasure, under other circ.u.mstances may appear as pain; and since he who chooses pleasure without distinction, will find impure pleasures always combined in his life with more or less of pain; his refutation of Cynicism he establishes by showing the necessary connection between virtue and true pleasure, showing that there is a true and enduring pleasure, the pleasure of reason, found in the possession of truth and of goodness, while a rational condition separate from all pleasure, cannot be the highest good of a finite being. It is most prominently by this distinction of a true and false, of a pure and impure pleasure, that Plato adjusts the controversy of the two Socratic schools.-A detailed exhibition of the Philebus we must here omit.-On the whole, in the Platonic apprehension of pleasure, we cannot but notice that same vacillation with which Plato every where treats of the relation between the corporeal and the spiritual, at one time considering the former as a hindrance to the latter, and at another as its serving instrument; now, regarding it as a concurring cause to the good, and then, as the ground of all evil; here, as something purely negative, and there, as a positive substratum which supports all the higher intellectual developments; and in conformity with this, pleasure is also considered at one time as something equivalent to a moral act, and to knowledge, and at another as the means and accidental consequence of the good.

2. VIRTUE.-In his theory of virtue, Plato is wholly Socratic. He holds fast to the opinion that it is science (_Protagoras_), and therefore, teachable (_Meno_), and as to its unity, it follows from the dialectical principle that the one can be manifold, or the manifold one, that, therefore, virtue must both be regarded as one, and also in a different respect, as many. Plato thus brings out prominently the union and connection of all virtues, and is fond of painting, especially in the introductory dialogues, some single virtue as comprising in itself the sum of all the rest. Plato follows for the most part the fourfold division of virtues, as popularly made; and first, in the Republic (IV.

441), he attempts a scientific derivation of them, by referring to each of the three parts of the soul its appropriate virtue. The virtue of the reason he calls prudence or wisdom, the directing or measuring virtue, without whose activity valor would sink to brute impulse, and calm endurance to stupid indifference; the virtue of spirit is valor, the help-meet of reason, or spirit (????) penetrated by science, which in the struggle against pleasure and pain, desire and fear, preserves the rational intelligence against the alarms with which sensuous desires, would seek to sway the soul; the virtue of the sensuous desires, and which has to reduce these within true and proper grounds, is temperance, and that virtue in fine to which belong the due regulation and mutual adjustment of the several powers of the soul, and which, therefore, const.i.tutes the bond and the unity of the three other virtues, is justice.

In this last conception, that of justice, all the elements of moral culture meet together and centre, exhibiting the moral life of the individual as a perfect whole, and then, by requiring an application of the same principle to communities, the moral consideration is advanced beyond the narrow circle of individual life. Thus is established the whole of the moral world-Justice "in great letters," the moral life in its complete totality, is the state. In this is first actualized the demand for the complete harmony of the human life. In and through the state comes the complete formation of matter for the reason.

3. THE STATE.-The Platonic state is generally regarded as an ideal or chimera, which it is impracticable to realize among men. This view of the case has even been ascribed to Plato, and it has been said that in his _Republic_ he attempted to sketch only a fine ideal of a state const.i.tution, while in the _Laws_ he traced out a practicable philosophy of the state from the standpoint of the common consciousness. But in the first place, this was not Plato's true meaning. Although he acknowledges that the state he describes cannot be found on earth, and has its archetype only in heaven, by which the philosopher ought to form himself (IX. 592), still he demands that efforts should be made to realize it here, and he even attempts to show the conditions and means under which such a state could be made actual, not overlooking in all this the defects arising from the different characters and temperaments of men. A composition, dissociated from the idea, could only appear untrue to a philosopher like Plato, who saw the actual and the true only in the idea; and the common view which supposes that he wrote his Republic in the full consciousness of its impracticability, mistakes entirely the standpoint of the Platonic philosophy. Still farther the question whether such a state as the Platonic is attainable and the best, is generally perverted. The Platonic state is the Grecian state-idea given in a narrative form. It is no vain and powerless ideal to picture the idea as a rational principle in every moment of the world's history, since the idea itself is that which is absolutely actual, that which is essential and necessary in existing things. The truly ideal _ought_ not to be actual, but _is_ actual, and the only actual; if an idea were too good for existence, or the empirical actuality too bad for it, then were this a fault of the ideal itself. Plato has not given himself up merely to abstract theories, the philosopher cannot leap beyond his age, but can only see and grasp it in its true content. This Plato has done. His standpoint is his own age. He looks upon the political life of the Greeks as then existing, and it is this life, exalted to its idea, which forms the real content of the Platonic Republic. Plato has here represented the Grecian morality in its substantial condition, If the Platonic Republic seems prominently an ideal which can never be realized, this is owing much less to its ideality than to the defects of the old political life. The most prominent characteristic of the h.e.l.lenic conception of the state, before the Greeks began to fall into unbridled licentiousness, was the constraint thrown upon personal subjective freedom, in the sacrifice of every individual interest to the absolute sovereignty of the state. With Plato also, the state is every thing. His political inst.i.tutions, so loudly ridiculed by the ancients, are only the undeniable consequences following from the very idea of the Grecian state, which allowed neither to the individual citizen nor to a corporation, any lawful sphere of action independent of itself.

The grand feature of the Platonic state is, as has been said, the exclusive sacrifice of the individual to the state, the reference of moral to political virtue. Since man cannot reach his complete development in isolation, but only as a member of an organic society (the state), Plato therefore concludes that the individual purpose should wholly conform to the general aim, and that the state must represent a perfect and harmonious unity, and be a counterpart of the moral life of the individual. In a perfect state all things, joy and sorrow, and even eyes, ears and hands, must be common to all, so that the social life would be as it were the life of one man. This perfect universality and unity, can only be actualized when every thing individual and particular falls away, and hence the difficulty of the Platonic Republic. Private property and domestic life (in place of which comes a community of goods and of wives), the duty of education, the choice of rank and profession, the arts and sciences, all these must be subjected and placed under the exclusive and absolute control of the state. The individual may lay claim only to that happiness which belongs to him as a const.i.tuent element of the state. From this point Plato goes down into the minutest particulars, and gives the closest directions respecting gymnastics and music, which form the two means of culture of the higher ranks; respecting the study of mathematics, and philosophy, the choice of stringed instruments, and the proper measure of verse; respecting bodily exercise and the service of women in war; respecting marriage settlements, and the age at which any one should study dialectics, marry, and beget children. The state with him is only a great educational establishment, a family in the ma.s.s.-Lyric poetry he would allow only under the inspection of competent judges. Epic and dramatic poetry, even Homer and Hesiod, should be banished from the state, since they rouse and lead astray the pa.s.sions, and give unworthy representations of the G.o.ds. Exhibitions of physical degeneracy or weakness should not be tolerated in the Platonic state; deformed and sickly infants should be abandoned, and food and attention should be denied to the sick.-In all this we find the chief ant.i.thesis of the ancient to the modern state. Plato did not recognize the will and choice of the individual, and yet the individual has a right to demand this.

The problem of the modern state has been to unite these two sides, to bring the universal end and the particular end of the individual into harmony, to reconcile the highest possible freedom of the conscious individual will, with the highest possible supremacy of the state.