activity the _Ethics_, so called, of Benedict Spinoza (1632-77) is certainly the most noteworthy; a work of five books on God, mind, emotions, bondage, and freedom--each with its special quota of axioms, propositions, corollaries, scholia, and the like, and the procedure of the whole amazingly consistent with that of Euclid. Excuse, also, a personal reminiscence. I can myself recall how in the enthusiasm of a first course in geometry I formulated a Euclidean proof of the proposition: Knowledge is power. I, too, had my axioms, my special demonstrations, my corollaries, and my final Q.E.D.'s. But any present-day resort to mathematics or its methods is only a shadow, or an echo, of the movement of the seventeenth century. At that time it was a movement of last resort and all the passion of a deceived intellect, of a mind given over to the most far-reaching doubts, and a disappointed faith, once more acquiring hope, was present in it. The truths and methods of mathematics--what but veracity incarnate, the very mind of God made manifest to mankind! Nor, furthermore, does it take much reflection to appreciate that mathematics was after all a very appropriate form for credible knowledge to take in a time of scepticism and of religion turning to purism. [p.179] Trustworthy knowledge of actual things--that is to say, real concrete knowledge--being held impossible, there was nothing left but knowledge of the strictly formal relations of things. Formal principles, just like those of mathematics, are altogether innocent of the confusion in actual things and persons, in particular events and current issues; and accordingly in the seventeenth century, just by reason of this innocence, they were peculiarly timely. Doubt seemed quite unable to touch them; controversy was turned to agreement before them; and even a truth-loving God, so to speak, could appeal to them in support of his right to rule the minds and the lives of men. You and I might question the reality of the things we count or the justice of the ratio between our wealth and the wealth of certain others in the world, but we could not easily question that two and two are four, or in matters of wealth that one thousand and two thousand dollars are in the same ratio as two million and four million. Such knowledge as this may not settle any actual quarrels that we have, for example, over the number of acres we own or the taxes we pay or the prices charged by our butchers or grocers; but what of that? The quarrels are idle any way, and our mathematical wisdom, being exact from the start and self-evident, is a basis of perfect agreement between man and man and men and God.