matters, a tabula rasa; but ignorance and prejudice and education all conspire to predispose us to some form of a priori philosophy, and most men who have not given hard thought to the subject hold fast, consciously or unconsciously, to belief in the universal and necessary conservation of energy, to belief in a necessary law of universal progress or evolution, to belief in the arbitrary and absolute freedom of the will, or to belief in some other a priori notion which they hold necessary and ultimate, or arbitrary and absolute.

"The maxim that metaphysical inquiries are barren of result," says Huxley, "and that the serious occupation of the mind with them is a mere waste of time and labor, finds much favor in the eyes of many persons who pride themselves on the possession of sound common sense; and we sometimes hear it enunciated by weighty authorities, as if its natural consequence, the suppression of such studies, had the force of a moral obligation."

"In this case, however, as in so many others, those who lay down the law seem to forget that a wise legislator will consider, not merely whether his proposed enactment is desirable, but whether obedience to it is possible. For if the latter question be answered negatively, the former is surely hardly worth debate."

"Here, in fact, lies the pith of the reply to those who would make metaphysics contraband of intellect. Whether it is desirable to place a prohibitory duty upon philosophical speculations or not, it is utterly impossible to prevent the importation of them into the mind. And it is not a little curious to observe that those who most loudly profess to abstain from such commodities are, all the while, unconscious consumers, on a great scale, of one or another of their multitudinous disguises or adulterations. With mouths full of the particular kind of heavily buttered toast which they affect, they inveigh against the eating of plain bread. In truth, the attempt to nourish the human intellect upon a diet which contains no metaphysics is about as hopeful as that of certain Eastern sages to nourish their bodies without destroying life."

"Everybody has heard the story of the pitiless microscopist, who ruined the peace of mind of one of these mild enthusiasts by showing him the animals moving in a drop of the water with which, in the innocency of his heart, he slaked his thirst; and the unsuspect

ing devotee of plain common sense may look for as unexpected a shock when the magnifier of severe logic reveals the germs, if not the full-grown shapes, of lively metaphysical postulates rampant amidst his most positive and matter of fact notions."1

Kant has shown, as Berkeley showed before him, that, instead of discovering truth, philosophy has only the modest merit of preventing error, and if men never made mistakes, but always reasoned wisely and acted rightly, we should little need to study the nature of knowledge; but while few men think, all have opinions; and there are certain perennial errors, idols, as Bacon calls them, which find in the mind of man a dwelling-place so congenial that the doctrine of idols. bears the same relation to the interpretation of nature as that of sophisms does to common logic.

As we are forced, by the imperfection of our nature, to study the principles of knowledge in order to guard ourselves from error, it makes little difference whether we call the principles of science metaphysical or not.

We speak of physical science, but it would surely be more repugnant to the usage of common speech to call the principles of science physical than to call them metaphysical; for, while the data of science are things known to sense, we must ask, with Berkeley, whether it is not certain that the principles of science are neither objects of sense nor of the imagination; whether they do not arise in the mind itself; whether the sensible world is anything more than the stimulus which calls forth the innate or latent powers of the mind. We assuredly have no sense-organ by which a principle may be perceived, except so far as we have by nature an organ of common sense. If the principles of science are perceived at all, rather than apprehended, they must be perceived by some inner sense, for which we know no sense-organ.

"As understanding perceiveth not, that is, doth not hear, or see, or feel, so sense knoweth not; and although the mind may use. both sense and fancy, as means whereby to arrive at knowledge, yet sense or soul, so far forth as sensitive, knoweth nothing. For, as it is rightly observed in the 'Theætetus' of Plato, science consisteth not in the passive perceptions, but in the reasoning about them."

1 Huxley, "Collected Essays," VI., pp. 288, 289.

Some, who so far agree with Plato, may be led to remind Berkeley that objects of sense are not only first considered by all men, but most considered by most men; and that the possession of opinions may be no evidence of reason.

Truth, he tells us, is the cry of all, but the game of few; and while there may be wisdom in a multitude of counsellors, Huxley reminds us that it is in but one or two of them.

Some may assert that, admitting that we have no sense-organ by which we perceive the relation between a pattering sound on the roof and a shower, the connection between the sound of rain and the falling drops is nevertheless physical and not mental; and that response to the order of nature is no evidence of reason, since we do not attribute judgment to the mimosa, which, stimulated by the falling drops, folds its leaves that the rain may reach. its roots.

They may also assert that, if the structure and history of all parts of our own organic mechanism were fully known, we should be able to show that the principles of science are physical; that we apprehend them because our minds are the ones which have survived the struggle for existence; and that these principles are no more than natural selection would lead one to expect; although we must ask whether we find in nature any reason why what we expect must happen; whether natural selection is an efficient cause, or only a generalization from experience; and whether experience is not itself a state of mind. We may point out that hope is not science, and that no one has, as yet, deduced the principles of science from brain anatomy; and we may ask whether, if this were accomplished, the anatomical structure of the brain, and of the other organs which we study by our senses, is not a thing perceived; whether perception is not mental; and whether a thing perceived by sense is not a phenomenon of mind. We may also ask whether proof that our organ of common sense has come about, like our eyes and ears, by the survival of the fittest, would tell us any more about the relation between mind and matter than our eyes and ears tell us now.

I am not able to answer the question whether, in ultimate analysis, the principles of science are physical or metaphysical. I know nothing about things ultimate. I do not know what the

relation between mind and matter is. I do not know whether the distinction between "things perceived by sense" and "relations apprehended by the mind" is founded in nature or not; but I am sure that natural knowledge is useful to me, that it is pleasant, and profitable, and instructive; and I must ask whether all this does not show that nature is intended.

This introductory summary of some of the topics I shall try to handle in the following lectures shows that these topics are neither few nor simple, nor am I so bold as to think that I can set any one of them on a firm foundation; for, like William Harvey, I do not wish what I say "to be taken as if I thought it a voice from an oracle"; although I hope it may "stir up the intellects of the studious to search more deeply into so obscure a subject."

I shall make no attempt at originality, but shall try to give you some of the results of my own study of the thoughts of others. Bacon tells us indeed that it is seldom in our power to both admire and surpass our author; since, like water, we rise not higher than the springhead whence we have descended; but I cannot agree with him that the attempt to put the thoughts of others in a new dress necessarily leads to the great injury of learning, for we often fail to master the wise thoughts of one who is not of our own times because his turn of words does not fit our point of view.

All I have to say is anticipated in invention and is varied only by the method of treating it. "For," like Montaigne, "I make others to relate (not after my own fantastie, but as it best falleth out) what I cannot so well express, either through unskill of language or want of judgement. I number not my borrowings, but I weigh them. And if I would have made their number to prevail, I would have had twice as many." But I trust that, Bacon notwithstanding, I have neither corrupted the labors of my predecessors nor contributed to the slavery of the sciences.

The lectures which follow have been prepared at different times, and for various reasons; but I hope that, as I have arranged them, they will exhibit unity of purpose, and the logical development of that purpose, which, in a word, is this: To show to them. who think with Berkeley, that "it is a hard thing to suppose

that right deductions from true principles should ever end in consequences which cannot be maintained or made consistent," that, in my opinion, there is nothing in the prevalence of mechanical conceptions of life, and of mind, or in the unlimited extension of these conceptions, to show that this hard thing to suppose is true.