PREFACE

IN two essays upon the life and work of Descartes, which will be found in the first volume of this collection, I have given some reasons for my conviction that he, if any one, has a claim to the title of father of modern philosophy. By this I mean that his general scheme of things, his conceptions of scientific method and of the conditions and limits of certainty, are far more essentially and characteristically modern than those of any of his immediate predecessors and successors. Indeed, the adepts in some branches of science had not fully mastered the import of his ideas so late as the beginning of this century.

The conditions of this remarkable position in the world of thought are to be found, as usual, primarily, in motherwit, secondarily, in circumstance. Trained by the best educators of the seventeenth century, the Jesuits; naturally endowed with a dialectic grasp and subtlety, which even they could hardly improve; and with a passion for getting at the truth, which even they could

hardly impair, Descartes possessed, in addition, a rare mastery of the art of literary expression. If the "Discours de la Méthode" had no other merits, it would be worth study for the sake of the luminous simplicity and sincerity of its style.

A mathematician of the very first rank, Descartes knew all that was to be known of mechanical and optical science in his day; he was a skilled and zealous practical anatomist; he was one of the first to recognise the prodigious importance of the discovery of his contemporary Harvey; and he penetrated more deeply into the physiology of the nervous system than any specialist in that science, for a century, or more, after his time. To this encyclopædic and yet first-hand acquaintance with the nature of things, he added an acquaintance with the nature of men (which is a much more valuable chapter of experience to philosophers than is commonly imagined), gathered in the opening campaigns of the Thirty Years' War, in wide travels, and amidst that brilliant French society in which Pascal was his worthy peer. Even a "Traité des Passions," to be worth anything, must be based upon observation and experiment; and, in this subject, facilities for laboratory practice of the most varied and extensive character were offered by the Paris of Mazarin and the Duchesses; the Paris, in which Descartes' great friend and ally, Father Mersenne, reckoned atheists by the thousand; and, in which,

political life touched the lowest depths of degradation, amidst the chaotic personal intrigues of the Fronde. Thus endowed, thus nurtured, thus tempered in the fires of experience, it is intelligible enough that a resolute, clear-headed man, haunted from his youth up, as he tells us, with an extreme desire to learn how to distinguish truth from falsehood, in order to see his way clearly and walk surely through life,1 should have early come to the conclusion, that the first thing to be done was to cast aside, at any rate temporarily, the crutches of traditional, or other, authority; and stand upright on his own feet, trusting to no support but that of the solid ground of fact.

It was in 1619, while meditating in solitary winter quarters, that Descartes (being about the same age as Hume when he wrote the "Treatise on Human Nature") made that famous resolution, to "take nothing for truth without clear knowledge that it is such," the great practical effect of which is the sanctification of doubt; the recognition that the profession of belief in propositions, of the truth of which there is no sufficient evidence, is immoral; the discrowning of authority as such; the repudiation of the confusion, beloved of sophists of all sorts, between free assent and mere piously gagged dissent; and the admission of the obligation to reconsider even one's axioms on due demand.

These, if I mistake not, are the notes of the

1 Discours de la Méthode. 1o Partie.

modern, as contrasted with the ancient spirit. It is true that the isolated greatness of Socrates was founded on intellectual and moral characteristics of the same order. He also persisted in demanding that no man should "take anything for truth without a clear knowledge that it is such,” and so constantly and systematically shocked authority and shook traditional security, that the fact of his being allowed to live for seventy years, if one comes to think of it, is evidence of the patient and tolerant disposition of his Athenian compatriots, which should obliterate the memory of the final hemlock. That which it may be well for us not to forget is, that the first-recorded judicial murder of a scientific thinker was compassed and effected, not by a despot, nor by priests, but was brought about by eloquent demagogues, to whom, of all men, thorough searchings of the intellect are most dangerous and therefore most hateful.

The first agnostic, the man who, so far as the records of history go, was the first to see that clear knowledge of what one does not know is just as important as knowing what one does know, had no true disciples; and the greatest of those who listened to him, if he preserved the fame of his master for all time, did his best to counteract the impulse towards intellectual clearness which Socrates gave. The Platonic philosophy is probably the grandest example of the unscientific use of the imagination extant; and it