And so, Theaetetus, knowledge is neither perception nor true opinion, nor yet definition accompanying true opinion. And I have shown that the children of your brain are not worth rearing. Are you still in labour, or have you brought all you have to say about knowledge to the birth? If you have any more thoughts, you will be the better for having got rid of these; or if you have none, you will be the better for not fancying that you know what you do not know. Observe the limits of my art, which, like my mother"s, is an art of midwifery; I do not pretend to compare with the good and wise of this and other ages.

And now I go to meet Meletus at the porch of the King Archon; but to-morrow I shall hope to see you again, Theodorus, at this place.

I. The saying of Theaetetus, that "Knowledge is sensible perception,"

may be a.s.sumed to be a current philosophical opinion of the age. "The ancients," as Aristotle (De Anim.) says, citing a verse of Empedocles, "affirmed knowledge to be the same as perception." We may now examine these words, first, with reference to their place in the history of philosophy, and secondly, in relation to modern speculations.

(a) In the age of Socrates the mind was pa.s.sing from the object to the subject. The same impulse which a century before had led men to form conceptions of the world, now led them to frame general notions of the human faculties and feelings, such as memory, opinion, and the like. The simplest of these is sensation, or sensible perception, by which Plato seems to mean the generalized notion of feelings and impressions of sense, without determining whether they are conscious or not.

The theory that "Knowledge is sensible perception" is the ant.i.thesis of that which derives knowledge from the mind (Theaet.), or which a.s.sumes the existence of ideas independent of the mind (Parm.). Yet from their extreme abstraction these theories do not represent the opposite poles of thought in the same way that the corresponding differences would in modern philosophy. The most ideal and the most sensational have a tendency to pa.s.s into one another; Heracleitus, like his great successor Hegel, has both aspects. The Eleatic isolation of Being and the Megarian or Cynic isolation of individuals are placed in the same cla.s.s by Plato (Soph.); and the same principle which is the symbol of motion to one mind is the symbol of rest to another. The Atomists, who are sometimes regarded as the Materialists of Plato, denied the reality of sensation.

And in the ancient as well as the modern world there were reactions from theory to experience, from ideas to sense. This is a point of view from which the philosophy of sensation presented great attraction to the ancient thinker. Amid the conflict of ideas and the variety of opinions, the impression of sense remained certain and uniform. Hardness, softness, cold, heat, etc. are not absolutely the same to different persons, but the art of measuring could at any rate reduce them all to definite natures (Republic). Thus the doctrine that knowledge is perception supplies or seems to supply a firm standing ground. Like the other notions of the earlier Greek philosophy, it was held in a very simple way, without much basis of reasoning, and without suggesting the questions which naturally arise in our own minds on the same subject.

(b) The fixedness of impressions of sense furnishes a link of connexion between ancient and modern philosophy. The modern thinker often repeats the parallel axiom, "All knowledge is experience." He means to say that the outward and not the inward is both the original source and the final criterion of truth, because the outward can be observed and a.n.a.lyzed; the inward is only known by external results, and is dimly perceived by each man for himself. In what does this differ from the saying of Theaetetus? Chiefly in this--that the modern term "experience," while implying a point of departure in sense and a return to sense, also includes all the processes of reasoning and imagination which have intervened. The necessary connexion between them by no means affords a measure of the relative degree of importance which is to be ascribed to either element. For the inductive portion of any science may be small, as in mathematics or ethics, compared with that which the mind has attained by reasoning and reflection on a very few facts.

II. The saying that "All knowledge is sensation" is identified by Plato with the Protagorean thesis that "Man is the measure of all things."

The interpretation which Protagoras himself is supposed to give of these latter words is: "Things are to me as they appear to me, and to you as they appear to you." But there remains still an ambiguity both in the text and in the explanation, which has to be cleared up. Did Protagoras merely mean to a.s.sert the relativity of knowledge to the human mind? Or did he mean to deny that there is an objective standard of truth?

These two questions have not been always clearly distinguished; the relativity of knowledge has been sometimes confounded with uncertainty.

The untutored mind is apt to suppose that objects exist independently of the human faculties, because they really exist independently of the faculties of any individual. In the same way, knowledge appears to be a body of truths stored up in books, which when once ascertained are independent of the discoverer. Further consideration shows us that these truths are not really independent of the mind; there is an adaptation of one to the other, of the eye to the object of sense, of the mind to the conception. There would be no world, if there neither were nor ever had been any one to perceive the world. A slight effort of reflection enables us to understand this; but no effort of reflection will enable us to pa.s.s beyond the limits of our own faculties, or to imagine the relation or adaptation of objects to the mind to be different from that of which we have experience. There are certain laws of language and logic to which we are compelled to conform, and to which our ideas naturally adapt themselves; and we can no more get rid of them than we can cease to be ourselves. The absolute and infinite, whether explained as self-existence, or as the totality of human thought, or as the Divine nature, if known to us at all, cannot escape from the category of relation.

But because knowledge is subjective or relative to the mind, we are not to suppose that we are therefore deprived of any of the tests or criteria of truth. One man still remains wiser than another, a more accurate observer and relater of facts, a truer measure of the proportions of knowledge. The nature of testimony is not altered, nor the verification of causes by prescribed methods less certain. Again, the truth must often come to a man through others, according to the measure of his capacity and education. But neither does this affect the testimony, whether written or oral, which he knows by experience to be trustworthy. He cannot escape from the laws of his own mind; and he cannot escape from the further accident of being dependent for his knowledge on others. But still this is no reason why he should always be in doubt; of many personal, of many historical and scientific facts he may be absolutely a.s.sured. And having such a ma.s.s of acknowledged truth in the mathematical and physical, not to speak of the moral sciences, the moderns have certainly no reason to acquiesce in the statement that truth is appearance only, or that there is no difference between appearance and truth.

The relativity of knowledge is a truism to us, but was a great psychological discovery in the fifth century before Christ. Of this discovery, the first distinct a.s.sertion is contained in the thesis of Protagoras. Probably he had no intention either of denying or affirming an objective standard of truth. He did not consider whether man in the higher or man in the lower sense was a "measure of all things." Like other great thinkers, he was absorbed with one idea, and that idea was the absoluteness of perception. Like Socrates, he seemed to see that philosophy must be brought back from "nature" to "truth," from the world to man. But he did not stop to a.n.a.lyze whether he meant "man" in the concrete or man in the abstract, any man or some men, "quod semper quod ubique" or individual private judgment. Such an a.n.a.lysis lay beyond his sphere of thought; the age before Socrates had not arrived at these distinctions. Like the Cynics, again, he discarded knowledge in any higher sense than perception. For "truer" or "wiser" he subst.i.tuted the word "better," and is not unwilling to admit that both states and individuals are capable of practical improvement. But this improvement does not arise from intellectual enlightenment, nor yet from the exertion of the will, but from a change of circ.u.mstances and impressions; and he who can effect this change in himself or others may be deemed a philosopher. In the mode of effecting it, while agreeing with Socrates and the Cynics in the importance which he attaches to practical life, he is at variance with both of them. To suppose that practice can be divorced from speculation, or that we may do good without caring about truth, is by no means singular, either in philosophy or life. The singularity of this, as of some other (so-called) sophistical doctrines, is the frankness with which they are avowed, instead of being veiled, as in modern times, under ambiguous and convenient phrases.

Plato appears to treat Protagoras much as he himself is treated by Aristotle; that is to say, he does not attempt to understand him from his own point of view. But he entangles him in the meshes of a more advanced logic. To which Protagoras is supposed to reply by Megarian quibbles, which destroy logic, "Not only man, but each man, and each man at each moment." In the arguments about sight and memory there is a palpable unfairness which is worthy of the great "brainless brothers,"

Euthydemus and Dionysodorus, and may be compared with the egkekalummenos ("obvelatus") of Eubulides. For he who sees with one eye only cannot be truly said both to see and not to see; nor is memory, which is liable to forget, the immediate knowledge to which Protagoras applies the term. Theodorus justly charges Socrates with going beyond the truth; and Protagoras has equally right on his side when he protests against Socrates arguing from the common use of words, which "the vulgar pervert in all manner of ways."

III. The theory of Protagoras is connected by Aristotle as well as Plato with the flux of Heracleitus. But Aristotle is only following Plato, and Plato, as we have already seen, did not mean to imply that such a connexion was admitted by Protagoras himself. His metaphysical genius saw or seemed to see a common tendency in them, just as the modern historian of ancient philosophy might perceive a parallelism between two thinkers of which they were probably unconscious themselves. We must remember throughout that Plato is not speaking of Heracleitus, but of the Herac.l.i.teans, who succeeded him; nor of the great original ideas of the master, but of the Eristic into which they had degenerated a hundred years later. There is nothing in the fragments of Heracleitus which at all justifies Plato"s account of him. His philosophy may be resolved into two elements--first, change, secondly, law or measure pervading the change: these he saw everywhere, and often expressed in strange mythological symbols. But he has no a.n.a.lysis of sensible perception such as Plato attributes to him; nor is there any reason to suppose that he pushed his philosophy into that absolute negation in which Herac.l.i.teanism was sunk in the age of Plato. He never said that "change means every sort of change;" and he expressly distinguished between "the general and particular understanding." Like a poet, he surveyed the elements of mythology, nature, thought, which lay before him, and sometimes by the light of genius he saw or seemed to see a mysterious principle working behind them. But as has been the case with other great philosophers, and with Plato and Aristotle themselves, what was really permanent and original could not be understood by the next generation, while a perverted logic carried out his chance expressions with an illogical consistency. His simple and n.o.ble thoughts, like those of the great Eleatic, soon degenerated into a mere strife of words. And when thus reduced to mere words, they seem to have exercised a far wider influence in the cities of Ionia (where the people "were mad about them") than in the life-time of Heracleitus--a phenomenon which, though at first sight singular, is not without a parallel in the history of philosophy and theology.

It is this perverted form of the Herac.l.i.tean philosophy which is supposed to effect the final overthrow of Protagorean sensationalism.

For if all things are changing at every moment, in all sorts of ways, then there is nothing fixed or defined at all, and therefore no sensible perception, nor any true word by which that or anything else can be described. Of course Protagoras would not have admitted the justice of this argument any more than Heracleitus would have acknowledged the "uneducated fanatics" who appealed to his writings. He might have said, "The excellent Socrates has first confused me with Heracleitus, and Heracleitus with his Ephesian successors, and has then disproved the existence both of knowledge and sensation. But I am not responsible for what I never said, nor will I admit that my common-sense account of knowledge can be overthrown by unintelligible Herac.l.i.tean paradoxes."

IV. Still at the bottom of the arguments there remains a truth, that knowledge is something more than sensible perception;--this alone would not distinguish man from a tadpole. The absoluteness of sensations at each moment destroys the very consciousness of sensations (compare Phileb.), or the power of comparing them. The senses are not mere holes in a "Trojan horse," but the organs of a presiding nature, in which they meet. A great advance has been made in psychology when the senses are recognized as organs of sense, and we are admitted to see or feel "through them" and not "by them," a distinction of words which, as Socrates observes, is by no means pedantic. A still further step has been made when the most abstract notions, such as Being and Not-being, sameness and difference, unity and plurality, are acknowledged to be the creations of the mind herself, working upon the feelings or impressions of sense. In this manner Plato describes the process of acquiring them, in the words "Knowledge consists not in the feelings or affections (pathemasi), but in the process of reasoning about them (sullogismo)."

Here, is in the Parmenides, he means something not really different from generalization. As in the Sophist, he is laying the foundation of a rational psychology, which is to supersede the Platonic reminiscence of Ideas as well as the Eleatic Being and the individualism of Megarians and Cynics.

V. Having rejected the doctrine that "Knowledge is perception," we now proceed to look for a definition of knowledge in the sphere of opinion.

But here we are met by a singular difficulty: How is false opinion possible? For we must either know or not know that which is presented to the mind or to sense. We of course should answer at once: "No; the alternative is not necessary, for there may be degrees of knowledge; and we may know and have forgotten, or we may be learning, or we may have a general but not a particular knowledge, or we may know but not be able to explain;" and many other ways may be imagined in which we know and do not know at the same time. But these answers belong to a later stage of metaphysical discussion; whereas the difficulty in question naturally arises owing to the childhood of the human mind, like the parallel difficulty respecting Not-being. Men had only recently arrived at the notion of opinion; they could not at once define the true and pa.s.s beyond into the false. The very word doxa was full of ambiguity, being sometimes, as in the Eleatic philosophy, applied to the sensible world, and again used in the more ordinary sense of opinion. There is no connexion between sensible appearance and probability, and yet both of them met in the word doxa, and could hardly be disengaged from one another in the mind of the Greek living in the fifth or fourth century B.C. To this was often added, as at the end of the fifth book of the Republic, the idea of relation, which is equally distinct from either of them; also a fourth notion, the conclusion of the dialectical process, the making up of the mind after she has been "talking to herself"

(Theat.).

We are not then surprised that the sphere of opinion and of Not-being should be a dusky, half-lighted place (Republic), belonging neither to the old world of sense and imagination, nor to the new world of reflection and reason. Plato attempts to clear up this darkness. In his accustomed manner he pa.s.ses from the lower to the higher, without omitting the intermediate stages. This appears to be the reason why he seeks for the definition of knowledge first in the sphere of opinion.

Hereafter we shall find that something more than opinion is required.

False opinion is explained by Plato at first as a confusion of mind and sense, which arises when the impression on the mind does not correspond to the impression made on the senses. It is obvious that this explanation (supposing the distinction between impressions on the mind and impressions on the senses to be admitted) does not account for all forms of error; and Plato has excluded himself from the consideration of the greater number, by designedly omitting the intermediate processes of learning and forgetting; nor does he include fallacies in the use of language or erroneous inferences. But he is struck by one possibility of error, which is not covered by his theory, viz. errors in arithmetic.

For in numbers and calculation there is no combination of thought and sense, and yet errors may often happen. Hence he is led to discard the explanation which might nevertheless have been supposed to hold good (for anything which he says to the contrary) as a rationale of error, in the case of facts derived from sense.

Another attempt is made to explain false opinion by a.s.signing to error a sort of positive existence. But error or ignorance is essentially negative--a not-knowing; if we knew an error, we should be no longer in error. We may veil our difficulty under figures of speech, but these, although telling arguments with the mult.i.tude, can never be the real foundation of a system of psychology. Only they lead us to dwell upon mental phenomena which if expressed in an abstract form would not be realized by us at all. The figure of the mind receiving impressions is one of those images which have rooted themselves for ever in language.

It may or may not be a "gracious aid" to thought; but it cannot be got rid of. The other figure of the enclosure is also remarkable as affording the first hint of universal all-pervading ideas,--a notion further carried out in the Sophist. This is implied in the birds, some in flocks, some solitary, which fly about anywhere and everywhere. Plato discards both figures, as not really solving the question which to us appears so simple: "How do we make mistakes?" The failure of the enquiry seems to show that we should return to knowledge, and begin with that; and we may afterwards proceed, with a better hope of success, to the examination of opinion.

But is true opinion really distinct from knowledge? The difference between these he seeks to establish by an argument, which to us appears singular and unsatisfactory. The existence of true opinion is proved by the rhetoric of the law courts, which cannot give knowledge, but may give true opinion. The rhetorician cannot put the judge or juror in possession of all the facts which prove an act of violence, but he may truly persuade them of the commission of such an act. Here the idea of true opinion seems to be a right conclusion from imperfect knowledge.

But the correctness of such an opinion will be purely accidental; and is really the effect of one man, who has the means of knowing, persuading another who has not. Plato would have done better if he had said that true opinion was a contradiction in terms.

a.s.suming the distinction between knowledge and opinion, Theaetetus, in answer to Socrates, proceeds to define knowledge as true opinion, with definite or rational explanation. This Socrates identifies with another and different theory, of those who a.s.sert that knowledge first begins with a proposition.

The elements may be perceived by sense, but they are names, and cannot be defined. When we a.s.sign to them some predicate, they first begin to have a meaning (onomaton sumploke logou ousia). This seems equivalent to saying, that the individuals of sense become the subject of knowledge when they are regarded as they are in nature in relation to other individuals.

Yet we feel a difficulty in following this new hypothesis. For must not opinion be equally expressed in a proposition? The difference between true and false opinion is not the difference between the particular and the universal, but between the true universal and the false. Thought may be as much at fault as sight. When we place individuals under a cla.s.s, or a.s.sign to them attributes, this is not knowledge, but a very rudimentary process of thought; the first generalization of all, without which language would be impossible. And has Plato kept altogether clear of a confusion, which the a.n.a.logous word logos tends to create, of a proposition and a definition? And is not the confusion increased by the use of the a.n.a.logous term "elements," or "letters"? For there is no real resemblance between the relation of letters to a syllable, and of the terms to a proposition.

Plato, in the spirit of the Megarian philosophy, soon discovers a flaw in the explanation. For how can we know a compound of which the simple elements are unknown to us? Can two unknowns make a known? Can a whole be something different from the parts? The answer of experience is that they can; for we may know a compound, which we are unable to a.n.a.lyze into its elements; and all the parts, when united, may be more than all the parts separated: e.g. the number four, or any other number, is more than the units which are contained in it; any chemical compound is more than and different from the simple elements. But ancient philosophy in this, as in many other instances, proceeding by the path of mental a.n.a.lysis, was perplexed by doubts which warred against the plainest facts.

Three attempts to explain the new definition of knowledge still remain to be considered. They all of them turn on the explanation of logos. The first account of the meaning of the word is the reflection of thought in speech--a sort of nominalism "La science est une langue bien faite." But anybody who is not dumb can say what he thinks; therefore mere speech cannot be knowledge. And yet we may observe, that there is in this explanation an element of truth which is not recognized by Plato; viz.

that truth and thought are inseparable from language, although mere expression in words is not truth. The second explanation of logos is the enumeration of the elementary parts of the complex whole. But this is only definition accompanied with right opinion, and does not yet attain to the certainty of knowledge. Plato does not mention the greater objection, which is, that the enumeration of particulars is endless; such a definition would be based on no principle, and would not help us at all in gaining a common idea. The third is the best explanation,--the possession of a characteristic mark, which seems to answer to the logical definition by genus and difference. But this, again, is equally necessary for right opinion; and we have already determined, although not on very satisfactory grounds, that knowledge must be distinguished from opinion. A better distinction is drawn between them in the Timaeus.

They might be opposed as philosophy and rhetoric, and as conversant respectively with necessary and contingent matter. But no true idea of the nature of either of them, or of their relation to one another, could be framed until science obtained a content. The ancient philosophers in the age of Plato thought of science only as pure abstraction, and to this opinion stood in no relation.

Like Theaetetus, we have attained to no definite result. But an interesting phase of ancient philosophy has pa.s.sed before us. And the negative result is not to be despised. For on certain subjects, and in certain states of knowledge, the work of negation or clearing the ground must go on, perhaps for a generation, before the new structure can begin to rise. Plato saw the necessity of combating the illogical logic of the Megarians and Eristics. For the completion of the edifice, he makes preparation in the Theaetetus, and crowns the work in the Sophist.

Many (1) fine expressions, and (2) remarks full of wisdom, (3) also germs of a metaphysic of the future, are scattered up and down in the dialogue. Such, for example, as (1) the comparison of Theaetetus"

progress in learning to the "noiseless flow of a river of oil"; the satirical touch, "flavouring a sauce or fawning speech"; or the remarkable expression, "full of impure dialectic"; or the lively images under which the argument is described,--"the flood of arguments pouring in," the fresh discussions "bursting in like a band of revellers."

(2) As ill.u.s.trations of the second head, may be cited the remark of Socrates, that "distinctions of words, although sometimes pedantic, are also necessary"; or the fine touch in the character of the lawyer, that "dangers came upon him when the tenderness of youth was unequal to them"; or the description of the manner in which the spirit is broken in a wicked man who listens to reproof until he becomes like a child; or the punishment of the wicked, which is not physical suffering, but the perpetual companionship of evil (compare Gorgias); or the saying, often repeated by Aristotle and others, that "philosophy begins in wonder, for Iris is the child of Thaumas"; or the superb contempt with which the philosopher takes down the pride of wealthy landed proprietors by comparison of the whole earth. (3) Important metaphysical ideas are: a.

the conception of thought, as the mind talking to herself; b. the notion of a common sense, developed further by Aristotle, and the explicit declaration, that the mind gains her conceptions of Being, sameness, number, and the like, from reflection on herself; c. the excellent distinction of Theaetetus (which Socrates, speaking with emphasis, "leaves to grow") between seeing the forms or hearing the sounds of words in a foreign language, and understanding the meaning of them; and d. the distinction of Socrates himself between "having" and "possessing"

knowledge, in which the answer to the whole discussion appears to be contained.

There is a difference between ancient and modern psychology, and we have a difficulty in explaining one in the terms of the other. To us the inward and outward sense and the inward and outward worlds of which they are the organs are parted by a wall, and appear as if they could never be confounded. The mind is endued with faculties, habits, instincts, and a personality or consciousness in which they are bound together. Over against these are placed forms, colours, external bodies coming into contact with our own body. We speak of a subject which is ourselves, of an object which is all the rest. These are separable in thought, but united in any act of sensation, reflection, or volition. As there are various degrees in which the mind may enter into or be abstracted from the operations of sense, so there are various points at which this separation or union may be supposed to occur. And within the sphere of mind the a.n.a.logy of sense reappears; and we distinguish not only external objects, but objects of will and of knowledge which we contrast with them. These again are comprehended in a higher object, which reunites with the subject. A mult.i.tude of abstractions are created by the efforts of successive thinkers which become logical determinations; and they have to be arranged in order, before the scheme of thought is complete. The framework of the human intellect is not the peculium of an individual, but the joint work of many who are of all ages and countries. What we are in mind is due, not merely to our physical, but to our mental antecedents which we trace in history, and more especially in the history of philosophy. Nor can mental phenomena be truly explained either by physiology or by the observation of consciousness apart from their history. They have a growth of their own, like the growth of a flower, a tree, a human being. They may be conceived as of themselves const.i.tuting a common mind, and having a sort of personal ident.i.ty in which they coexist.

So comprehensive is modern psychology, seeming to aim at constructing anew the entire world of thought. And prior to or simultaneously with this construction a negative process has to be carried on, a clearing away of useless abstractions which we have inherited from the past. Many erroneous conceptions of the mind derived from former philosophies have found their way into language, and we with difficulty disengage ourselves from them. Mere figures of speech have unconsciously influenced the minds of great thinkers. Also there are some distinctions, as, for example, that of the will and of the reason, and of the moral and intellectual faculties, which are carried further than is justified by experience. Any separation of things which we cannot see or exactly define, though it may be necessary, is a fertile source of error. The division of the mind into faculties or powers or virtues is too deeply rooted in language to be got rid of, but it gives a false impression. For if we reflect on ourselves we see that all our faculties easily pa.s.s into one another, and are bound together in a single mind or consciousness; but this mental unity is apt to be concealed from us by the distinctions of language.

A profusion of words and ideas has obscured rather than enlightened mental science. It is hard to say how many fallacies have arisen from the representation of the mind as a box, as a "tabula rasa," a book, a mirror, and the like. It is remarkable how Plato in the Theaetetus, after having indulged in the figure of the waxen tablet and the decoy, afterwards discards them. The mind is also represented by another cla.s.s of images, as the spring of a watch, a motive power, a breath, a stream, a succession of points or moments. As Plato remarks in the Cratylus, words expressive of motion as well as of rest are employed to describe the faculties and operations of the mind; and in these there is contained another store of fallacies. Some shadow or reflection of the body seems always to adhere to our thoughts about ourselves, and mental processes are hardly distinguished in language from bodily ones. To see or perceive are used indifferently of both; the words intuition, moral sense, common sense, the mind"s eye, are figures of speech transferred from one to the other. And many other words used in early poetry or in sacred writings to express the works of mind have a materialistic sound; for old mythology was allied to sense, and the distinction of matter and mind had not as yet arisen. Thus materialism receives an illusive aid from language; and both in philosophy and religion the imaginary figure or a.s.sociation easily takes the place of real knowledge.

Again, there is the illusion of looking into our own minds as if our thoughts or feelings were written down in a book. This is another figure of speech, which might be appropriately termed "the fallacy of the looking-gla.s.s." We cannot look at the mind unless we have the eye which sees, and we can only look, not into, but out of the mind at the thoughts, words, actions of ourselves and others. What we dimly recognize within us is not experience, but rather the suggestion of an experience, which we may gather, if we will, from the observation of the world. The memory has but a feeble recollection of what we were saying or doing a few weeks or a few months ago, and still less of what we were thinking or feeling. This is one among many reasons why there is so little self-knowledge among mankind; they do not carry with them the thought of what they are or have been. The so-called "facts of consciousness" are equally evanescent; they are facts which n.o.body ever saw, and which can neither be defined nor described. Of the three laws of thought the first (All A = A) is an identical proposition--that is to say, a mere word or symbol claiming to be a proposition: the two others (Nothing can be A and not A, and Everything is either A or not A) are untrue, because they exclude degrees and also the mixed modes and double aspects under which truth is so often presented to us. To a.s.sert that man is man is unmeaning; to say that he is free or necessary and cannot be both is a half truth only. These are a few of the entanglements which impede the natural course of human thought. Lastly, there is the fallacy which lies still deeper, of regarding the individual mind apart from the universal, or either, as a self-existent ent.i.ty apart from the ideas which are contained in them.

In ancient philosophies the a.n.a.lysis of the mind is still rudimentary and imperfect. It naturally began with an effort to disengage the universal from sense--this was the first lifting up of the mist. It wavered between object and subject, pa.s.sing imperceptibly from one or Being to mind and thought. Appearance in the outward object was for a time indistinguishable from opinion in the subject. At length mankind spoke of knowing as well as of opining or perceiving. But when the word "knowledge" was found how was it to be explained or defined? It was not an error, it was a step in the right direction, when Protagoras said that "Man is the measure of all things," and that "All knowledge is perception." This was the subjective which corresponded to the objective "All is flux." But the thoughts of men deepened, and soon they began to be aware that knowledge was neither sense, nor yet opinion--with or without explanation; nor the expression of thought, nor the enumeration of parts, nor the addition of characteristic marks. Motion and rest were equally ill adapted to express its nature, although both must in some sense be attributed to it; it might be described more truly as the mind conversing with herself; the discourse of reason; the hymn of dialectic, the science of relations, of ideas, of the so-called arts and sciences, of the one, of the good, of the all:--this is the way along which Plato is leading us in his later dialogues. In its higher signification it was the knowledge, not of men, but of G.o.ds, perfect and all sufficing:--like other ideals always pa.s.sing out of sight, and nevertheless present to the mind of Aristotle as well as Plato, and the reality to which they were both tending. For Aristotle as well as Plato would in modern phraseology have been termed a mystic; and like him would have defined the higher philosophy to be "Knowledge of being or essence,"--words to which in our own day we have a difficulty in attaching a meaning.

Yet, in spite of Plato and his followers, mankind have again and again returned to a sensational philosophy. As to some of the early thinkers, amid the fleetings of sensible objects, ideas alone seemed to be fixed, so to a later generation amid the fluctuation of philosophical opinions the only fixed points appeared to be outward objects. Any pretence of knowledge which went beyond them implied logical processes, of the correctness of which they had no a.s.surance and which at best were only probable. The mind, tired of wandering, sought to rest on firm ground; when the idols of philosophy and language were stripped off, the perception of outward objects alone remained. The ancient Epicureans never asked whether the comparison of these with one another did not involve principles of another kind which were above and beyond them. In like manner the modern inductive philosophy forgot to enquire into the meaning of experience, and did not attempt to form a conception of outward objects apart from the mind, or of the mind apart from them.

Soon objects of sense were merged in sensations and feelings, but feelings and sensations were still una.n.a.lyzed. At last we return to the doctrine attributed by Plato to Protagoras, that the mind is only a succession of momentary perceptions. At this point the modern philosophy of experience forms an alliance with ancient scepticism.

The higher truths of philosophy and religion are very far removed from sense. Admitting that, like all other knowledge, they are derived from experience, and that experience is ultimately resolvable into facts which come to us through the eye and ear, still their origin is a mere accident which has nothing to do with their true nature. They are universal and unseen; they belong to all times--past, present, and future. Any worthy notion of mind or reason includes them. The proof of them is, 1st, their comprehensiveness and consistency with one another; 2ndly, their agreement with history and experience. But sensation is of the present only, is isolated, is and is not in successive moments. It takes the pa.s.sing hour as it comes, following the lead of the eye or ear instead of the command of reason. It is a faculty which man has in common with the animals, and in which he is inferior to many of them.

The importance of the senses in us is that they are the apertures of the mind, doors and windows through which we take in and make our own the materials of knowledge. Regarded in any other point of view sensation is of all mental acts the most trivial and superficial. Hence the term "sensational" is rightly used to express what is shallow in thought and feeling.

We propose in what follows, first of all, like Plato in the Theaetetus, to a.n.a.lyse sensation, and secondly to trace the connexion between theories of sensation and a sensational or Epicurean philosophy.

Paragraph I. We, as well as the ancients, speak of the five senses, and of a sense, or common sense, which is the abstraction of them. The term "sense" is also used metaphorically, both in ancient and modern philosophy, to express the operations of the mind which are immediate or intuitive. Of the five senses, two--the sight and the hearing--are of a more subtle and complex nature, while two others--the smell and the taste--seem to be only more refined varieties of touch. All of them are pa.s.sive, and by this are distinguished from the active faculty of speech: they receive impressions, but do not produce them, except in so far as they are objects of sense themselves.

Physiology speaks to us of the wonderful apparatus of nerves, muscles, tissues, by which the senses are enabled to fulfil their functions. It traces the connexion, though imperfectly, of the bodily organs with the operations of the mind. Of these latter, it seems rather to know the conditions than the causes. It can prove to us that without the brain we cannot think, and that without the eye we cannot see: and yet there is far more in thinking and seeing than is given by the brain and the eye.

It observes the "concomitant variations" of body and mind. Psychology, on the other hand, treats of the same subject regarded from another point of view. It speaks of the relation of the senses to one another; it shows how they meet the mind; it a.n.a.lyzes the transition from sense to thought. The one describes their nature as apparent to the outward eye; by the other they are regarded only as the instruments of the mind.

It is in this latter point of view that we propose to consider them.

The simplest sensation involves an unconscious or nascent operation of the mind; it implies objects of sense, and objects of sense have differences of form, number, colour. But the conception of an object without us, or the power of discriminating numbers, forms, colours, is not given by the sense, but by the mind. A mere sensation does not attain to distinctness: it is a confused impression, sugkechumenon ti, as Plato says (Republic), until number introduces light and order into the confusion. At what point confusion becomes distinctness is a question of degree which cannot be precisely determined. The distant object, the undefined notion, come out into relief as we approach them or attend to them. Or we may a.s.sist the a.n.a.lysis by attempting to imagine the world first dawning upon the eye of the infant or of a person newly restored to sight. Yet even with them the mind as well as the eye opens or enlarges. For all three are inseparably bound together--the object would be nowhere and nothing, if not perceived by the sense, and the sense would have no power of distinguishing without the mind.