The characters in Homer are marked by this incredulous disposition in direct proportion to their general wisdom. When Agamemnon relates his dream to the assembled chiefs, Nestor dryly observes that if anyone of less authority had told them such a story they would have immediately rejected it as untrue. Hector’s outspoken contempt for augury is well known; and his indifference to the dying words of Patroclus is equally characteristic. In the Odyssey, Alcinous pointedly distinguishes his guest from the common run of travellers, whose words deserve no credit. That Telemachus should tell who is his father, with the uncomplimentary reservation that he has only his mother’s word for it, is evidently meant as a proof of the young man’s precocious shrewdness; and it is with the utmost difficulty that Penelope herself is persuaded of her husband’s identity. So in the Agamemnon of Aeschylus, nothing less than the report of an eye-witness will convince the Chorus of old men that Troy has really fallen.[218] Finally, to complete the list of examples afforded independently of philosophical reflection, Herodotus repeatedly expresses disbelief in the stories told him, or, what is more remarkable, holds his judgment in suspense with regard to their veracity.
Scepticism, as a philosophical principle, is alien from early Greek thought; but it is pervaded by a negative tendency exhibited in four different directions, all converging towards the later attitude of suspensive doubt. There are sharp criticisms on the popular mythology; there are protests against the ascription of reality to sensible appearances; there are contemptuous references on the part of some philosophers to the opinions held by others; and there are occasional lamentations over the difficulty of getting at any truth at all. The importance, however, of these last utterances has been considerably exaggerated both in ancient and modern times. For, in some instances, they are attributable solely to the distrust of sense-perception, and in others they seem to express nothing more than a passing mood against which we must set the dogmatic conclusions elsewhere enunciated with perfect confidence by the same thinkers.[219] At the same time, we have to note, as an illustration of the standing connexion between theological belief and that kind of scepticism which is shown by distrust in man’s power of discovering the truth for himself, that the strongest expressions of such a distrust are to be found in the two most religious of the pre-Socratic thinkers, Xenophanes and Empedocles.
III.
A new period begins with the Greek Humanists. We use this term in preference to that of Sophists, because, as has been shown, in specially dealing with the subject, half the teachers known under the latter denomination made it their business to popularise physical science and to apply it to morality, while the other half struck out an entirely different line, and founded their educational system on the express rejection of such investigations; their method being, in this respect, foreshadowed by the greatest poet of the age, who concentrates all his attention on the workings of the human mind, and followed by its greatest historian, with whom a similar study takes the place occupied by geography and natural history in the work of Herodotus. This absorption in human interests was unfavourable alike to the objects and to the methods of previous enquiry: to the former, as a diversion from the new studies; to the latter, as inconsistent with the flexibility and many-sidedness of conscious mind. Hence the true father of philosophical scepticism was Protagoras. With him, for the first time, we find full expression given to the proper sceptical attitude, which is one of suspense and indifference as opposed to absolute denial. He does not undertake to say whether the gods exist or not. He regards the real essence of Nature as unknowable, on account of the relativity which characterises all sensible impressions. And wherever opinions are divided, he undertakes to provide equally strong arguments for both sides of the question. He also anticipates the two principal tendencies exhibited by all future scepticism in its relation to practice. One is its devotion to humanity, under the double form of exclusive attention to human interests, and great mildness in the treatment of human beings. The other is a disposition to take custom and public opinion, rather than any physical or metaphysical law, for the standard and sanction of morality. Such scepticism might for the moment be hostile to religion; but a reconciliation was likely to be soon effected between them.
The famous theses of Gorgias were quoted in a former chapter as an illustration of the tactics pursued by Greek Humanism in its controversy with physical science. They must be noticed again in the present connexion, on account of their bearing on the development of scepticism, and as having inaugurated a method of reasoning often employed in subsequent attacks, directed, not against the whole of knowledge, but against particular parts of it. The scepticism of Protagoras rested on the assumption that there is an external reality from the reaction of which with mind all our perceptions proceed. Neither of these two factors can be known apart from the other, and as both are in a constant flux, our knowledge of the resulting compound at one time does not show what it has been or will be at another time. But Gorgias altogether denied the existence of any objective reality; and he attempted to disprove it by an analytical instead of a synthetic argument, laying down a series of disjunctive propositions, and upsetting the different alternatives in succession. Existence must be either something or nothing, or both together; and if something, it must be either finite or infinite, or both, and either one or many, or both. His argument against an infinite existence is altogether futile; but it serves to illustrate the undeveloped state of reflection at that period. The eternity of the world is confounded with its unlimited extension in space: and this hypothesis, again, is met by the transparent quibble that the world, not being in any one place, must be nowhere or not at all. And the alternative that the world has not always existed is refuted by the unproved assumption, which, apparently, no Greek philosopher ever thought of disputing, that nothing can begin without being caused by something else. Still, however contemptible such reasonings may seem, it is obvious that in them we have the first crude form of the famous antinomies by which Kant long afterwards sought to prove the impossibility of a world existing in space and time apart from a percipient subject, and which have since been used to establish in a more general way the unknowability of existence as such. It will also be observed that the sceptical arguments respectively derived from the relativity of thought and from the contradictions inherent in its ultimate products are run together by modern agnostics. But no reason that we can remember has ever been given to show that an idea is necessarily subjective because it is self-contradictory.
The second thesis of Gorgias was that, even granting the world to exist, it could not possibly be known. Here the reasoning is unexpectedly weak. Because all thoughts do not represent facts,—as, for example, our ideas of impossible combinations, like chariots running over the sea,—it is assumed that none do. But the problem how to distinguish between true and false ideas was raised, and it was round this that the fiercest battle between dogmatists and sceptics subsequently raged. And in the complete convertibility of consciousness and reality postulated by Gorgias, we may find the suggestion of a point sometimes overlooked in the automatist controversy—namely, that the impossibility, if any, of our acting on the material world reciprocally involves the impossibility of its acting on us, in so far as we are conscious beings. If thought cannot be translated into movement, neither can movement be translated into thought.
The third thesis maintains that, granting the world to exist and to be knowable, one man cannot communicate his knowledge to another; for, the different classes of sensations being heterogeneous, a visual or tactual impression on our consciousness cannot be conveyed by an auditory impression on the consciousness of someone else. This difficulty has been completely overcome by the subsequent progress of thought. We cannot, it is true, directly communicate more than a few sensations to one another; but by producing one we may call up others with which it has become associated through previous experience. And the great bulk of our knowledge has been analysed into relations of co-existence, succession, and resemblance, which are quite independent of the particular symbols employed to transmit them from one mind to another.[220]
The scepticism of Aristippus and the Cyrenaics mediated between the views of Protagoras and those of Gorgias, while marking an advance on both. According to this school, we know nothing beyond our own feelings, and it must be left undecided whether they are caused by an external reality or not. Nor can the feelings of one individual justify us in reasoning to the existence of similar feelings in the mind of another individual.[221] It might be objected that the arguments advanced in support of the latter assertion are suicidal, for they are derived from the abnormal states of consciousness accompanying particular diseases, or else from the divergences of taste exhibited by different individuals even when in good health,—an apparent admission that we are sufficiently well acquainted with the phenomena in question to institute a comparison between them, which, by hypothesis, is impossible. And this is, in fact, the method by which Mr. Herbert Spencer has endeavoured to upset the whole theory of subjective idealism, as involving at every step an assumption of the very realities that it professes to deny. But the Cyrenaic and the modern idealist have a perfect right to show that the assumptions of their adversaries are self-contradictory; and the readiest way of so doing is to reason from them as if they were true. The real answer to that extreme form of idealism which denies the possibility of making known our feelings to each other is that, our bodies being similarly constructed and responding to similar impressions by similar manifestations, I have the same sort of warrant for assuming that your states of consciousness are like mine that I have for assuming you to exist at all. The inference must, of course, be surrounded by proper precautions, such as are seldom used by unscientific reasoners. We must make sure that the structure is the same and that the excitement is the same, or that their differences, if any, are insignificant, before we can attribute the same value to the same manifestations of feeling on the part of different persons; but that this can be done, at least in the case of the elementary sensations, is shown by the easy detection of such anomalies as colour-blindness where they exist.
With Socrates and Plato, scepticism exhibits itself under two new aspects: as an accompaniment of religious belief, and as an element of constructive thought. Thus they represent both the good and the bad side of this tendency: the aspect under which it is a help, and the aspect under which it is a hindrance to scientific investigation. With both philosophers, however, the restriction or negation of human knowledge was a consequence rather than a cause of their theological convictions; nor do they seem to have appreciated its value as a weapon in the controversy with religious unbelief. When Socrates represented the irreconcilable divergence in the explanations of Nature offered by previous thinkers as a sufficient condemnation of their several pretensions, he did not set this fact against the arguments by which a Xenophanes had similarly endeavoured to overthrow the popular mythology; but he looked on it as a fatal consequence of their insane presumption in meddling with the secrets of the gods. On one occasion only, when explaining to Euthydêmus that the invisibility of the gods is no reason for doubting their existence, he argues, somewhat in Butler’s style, that our own minds, whose existence we cannot doubt, are equally invisible.[222] And the Platonic Socrates makes it his business to demonstrate the universality of human ignorance, not as a caution against dogmatic unbelief, but as a glorification of the divine knowledge; though how we come to know that there is any such knowledge he leaves utterly unexplained.
In Plato’s Parmenides we have to note the germ of a new dialectic. There it is suggested that we may overcome the difficulties attending a particular theory—in this instance the theory of self-existing ideas—by considering how much greater are the difficulties which would ensue on its rejection. The arguments advanced by Zeno the Eleatic against the reality of motion are mentioned as a case in point; and Plato proceeds to illustrate his proposed method by showing what consequences respectively follow if we first assume the existence, and then the non-existence of the One; but the whole analysis seems valueless for its immediate purpose, since the resulting impossibilities on either side are left exactly balanced; and Plato does not, like some modern metaphysicians, call in our affections to decide the controversy.