Thus the interpretation of reality in terms of mathematics and "unalterable law," is artificial; an abstract way of thinking which deals not with reality itself but with certain deliberately selected aspects of it. RISE OF A NEW PHILOSOPHY.--This examination of the principles of natural science was the beginning of what afterwards proved to be a revolution in thought. What had been more or less negative criticism in Mach and Boutroux, became the basis of a new philosophy in the hands of William James and Bergson. The names, and even the ideas, of these two original thinkers are familiar far outside strictly philosophical circles, and it will almost be possible to presume upon a certain acquaintance with them on the part of our readers. WILLIAM JAMES.--James himself, like Mach, was led to philosophy by the road of scientific investigation. He was a psychologist, and it is as the author of his _Principles of Psychology_ that his name will be remembered. This work is notable as containing the first complete application of the Darwinian theory to the evolution of mind. Mental action is there represented as a capacity developed by the organism to enable it to deal with its environment. As an exponent of James puts it: "The mind, like an antenna, feels its way for the organism. It gropes about, advances and recoils, making many random efforts and many failures; always urged into taking the initiative and doomed to success or failure in some hour of trial."[53] The corollary which attaches to propositions of this kind is that knowledge in all its varieties and developments arises from _practical needs_. And the mind (here is an echo of Mach) _selects_ those aspects of reality which concern it, and out of that selected material makes up a new (mental) world of its own. Which world is far from being a "picture" of reality, but which is "symbolic" of it (here is another memory of Mach).[54] This view obviously cuts the ground from under dogmatic materialism. The world which that philosophy regards as _reality_, is, to the critical eye, a collection of abstractions, a mental creation arising out of the practical needs of life. HENRI BERGSON.--This line of criticism, that of the evolutionary psychologist, opened up by James, has been carried to extreme lengths by the French philosopher Bergson. "Dig to the very roots of nature and of mind" is his advice. He begins by asking, How, as a matter of history, has human intellect developed? He then, and then only, proceeds to put the question (which uncritical thinkers always put _first_), What can the intellect do for us?