ternal world, the belief in God, nay even the belief in the existence of our own minds-as distinct from the hosts of ideas which flit through them-is matter, not of knowledge, but of blind instinct, which science can in a measure account for, but which it must in vain attempt to justify.—If substances are thus to be subjectively interpreted, so also are relations. These are but various ways of comparing ideas; or, more precisely, they are complex ideas formed from simpler ideas by the inexplicable process of comparison. Certain classes of relations—for example, the equality or inequality of quantities or numbers-are found to be completely determined by the ideas compared; that is to say, while these ideas are unchanged the relation remains the same. Such relations give rise to no peculiar problem. They are expressed by universal propositions, from which valid deductions may be made; and in the cases above mentioned the deductions are so extensive as to constitute special sciences. The other class of relations (those of space and time, identity, and causality) are more remarkable. The utmost analysis of any acknowledged cause and effect (for example) will reveal no quality or combination of qualities in either or both that determines why the one should be thought to produce the other. And the most exact attention to two bell-tones will disclose no shade of difference between them that could account for the one's being heard as preceding or following the other. In every such case, therefore, the relation must be supposed to be determined by other accompanying sensations, feelings, or ideas. Thus the second of two bell-tones may be accompanied by a memory-image of the first. In the case of causality, the relation depends upon a feeling of 'necessary connection,' which accompanies the habitual movement of the imagination from one event to another, when they have frequently been observed to occur in close succession and uniform order. Causal necessity is therefore by no means equivalent to logical implication. Nor is it a property of the operations

The inclusion of identity in the list is at first sight surprising. But it is meant that at most a complete resemblance can be actually determined by the comparison of two ideas. The interpretation of this as identity is another thing.

of nature, in themselves considered, but a property of our imaginations projected forth upon them.

Such were the two great types of philosophical thought which prevailed among the leading minds of Europe for five generations. We are aware how scanty has been our exposition, and how much that is of first class importance has been passed over. And yet, could we have contrived it, we should have cut the account still shorter. For our object has been simply to present the main lines of cleavage with all the distinctness of a glaring contrast. As we conceive it, the difference is essentially one between two scientific ideals, gained from the two sciences which were in most active progress at that time. Well-known parallels of greater or less suggestiveness are to be found in the influence of the science of mechanics upon Kant, of the history of civilization upon Hegel, of biology upon the ethical speculation of the halfcentury since the Origin of Species, and of comparative and social psychology upon many thinkers of today.

In this connection it is interesting to note that of the greater English empiricists not one was a mathematician. Berkeley, indeed, had a more than ordinarily good training in mathematics, and showed a very keen interest in such studies. His earliest published writings were upon mathematical subjects. But his greatness lay elsewhere. Hutcheson, more than any other of the school, was influenced in his thought by mathematical conceptions-sometimes in a very grotesque fashion. But this was only in the details of his system; its general structure was wholly psychological. Equally interesting is the impermeability of Leibniz to the influences of the new psychology. For Leibniz, among all philosophers, ancient and modern, is conspicuous both for the breadth of his sympathies and the clearness of his critical insight; and his literary life overlapped not only Locke's but Berkeley's. Locke, indeed, he understood-except where a spirit of prophecy was necessary to understand him; but in Berkeley's epoch-making work he could see nothing at all. And in his own psychology

the significance of introspection as a method of analysis finds scant recognition. Consider for a moment the central feature of his psychological theory, the conception of subconscious sensations (or petites perceptions, as he called them). By what manner of argument is the assumption of their existence supported? We hear the sound of the waves beating upon the shore. The waves are made of tiny drops, the separate sounds of which we cannot distinguish. But yet we may be assured that each drop makes some sound; for if the drops were silent the whole ocean would be dumb. What would Berkeley have thought of that? Leibniz's followers endeavored to make room for the new psychology by giving it a place alongside of the old, distinguishing thus between empirical and rational psychology. This was as far as appreciation of it went.

In insisting thus upon the contrasting characteristics of rationalism and empiricism, we have had an ulterior object in view; namely, to prepare the way for an exposition of their common presuppositions. To have attempted this latter task without such preparation would have been doubly dangerous; first, by exposing us to the criticism, that we were losing sight of differences and endeavoring to confound well-established distinctions; and, secondly, by putting us in the position of one who is arguing for a thesis and hence is involuntarily led to suppress or distort the facts which tend to weaken his contention. Whereas now we can at least pretend to candor, and can prosecute our discussion without fearing that we shall be accused of a partisan interest in its outcome.

CHAPTER II

THE COMMON BASIS OF EMPIRICISM AND RATIONALISM

I. THE CERTAINTY OF IMMEDIATE EXPERIENCE

A very pointed discussion has recently been carried on, concerning the proper standpoint to be assumed in the criticism of the philosophers and philosophical schools of the past. How far ought we to forget the increased knowledge which the years have brought us, and, entering into the life of the past, to judge of the value of its theories only in their own terms? Such conduct seems a commendable generosity to old friends. But are the philosophers more our friends than truth; and can the claims of truth be satisfied if the standards by which we judge be anything less than established fact and cogent demonstration? The question has had a two-fold bearing, according as the reputation of the thinker or the continued consideration to be given to his work has been regarded as at stake. On the first score, the historically minded critics have a comparatively easy case to defend. Few men of sense are now inclined, for example, to begrudge Descartes his fame as a natural philosopher, because his vortextheory of creation or his hypothesis of animal spirits flowing through hollow nerve-channels has been definitely abandoned. The greatness of the scientist does not depend wholly on his permanent achievements. But, on the second score, the justice of the historical attitude is not so clear; and many a learned critic must have felt the accusation rankling within him, that he had debased the study of philosophy to a mere æsthetic appreciation of harmonious and grand ideas.

There are several reasons, nevertheless, which constrain us to the opinion, that with doctrines, as with men, the sympathetic criticism is the best. In the first place, the observation is familiar, that the endeavor to do bare justice is a constant source of

rank injustice,—that the habit of checking up each paragraph of an author with the reflection, “After all, is this true?" is to ensure constant misinterpretation. For interpretation, at any rate, must be historical; and the mental agility to skip back and forth over the interval of even a century is not human. Even the canons of sound deduction, extra-temporal as their validity may be, can seldom be applied by the critic without a thought as to the scientific atmosphere that may have enveloped and given color to the naked words that remain. The men who find fallacies in Plato are generally superficial students. No man puts on paper anything approaching a complete record of his thought. For one premise expressed, there are ten that writer and reader alike supply from their common fund of assumptions. And the inadequacy of the expression is only magnified when the writer departs from the tradition of his school, correcting the assumptions which both he and his reader have alike regarded as indubitable. For though the need of free and full expression is sensibly increased, the possibility of real intellectual intercourse is as much diminished. One is tempted to remark that no man ever understands a philosophical doctrine who has not been previously led to a similar hypothesis in the course of his own reflections. This, at any rate, we may safely say: first, that to discover a formal fallacy in the reasonings of one of the great masters is, generally speaking, equivalent to revealing one's own lack of comprehension; and, secondly, that when the existence of the fallacy is fully established it remains probable that the particular line of argument thus demolished has in reality little to do with the acceptance of its conclusion. The really significant errors of the philosophers are upon a far more magnificent scale. They have their sources in peculiar limitations of character and environment; and in their consequences they affect the entire worldview. The well attested fallacy is, rightly regarded, but one surface indication among the many that must be patiently sought out, of vast underlying strata of thought.

True it is, indeed, that however frankly one may in general