Many people, including some scientific men, take science too seriously. They think that science gives a far more comprehensive picture of reality than it really does. There have been philosophers who have gone so far as to suppose that those factors of experience that science does not find it necessary to talk about do not really exist. This is the basis of the belief that colours, sounds, and scents have no “objective” existence; they exist only in the mind, whereas such qualities as mass and extension are supposed to exist independently of the mind. It is true that science does not find it necessary to refer to colours, sounds, and scents in giving its description of nature, whereas it does find it necessary to refer to mass and extension. But that does not prove that the former qualities are not as real as the latter, are not as indubitably part of the universe. The scientific concepts have by no means proved themselves adequate to account for the whole of experience. Nearly everything of real importance to man lies at present outside science. The fact is that science was undertaken as an intellectual adventure: it was an attempt to find out how far nature could be described in mathematical terms. Certain primary conceptions――time, space, mass, force, and so on――all of which can be defined mathematically, were adopted, and it became a highly absorbing game to find out how much of what goes on around us could be described, mathematically, in terms of these conceptions. The success of this effort has been so astonishing that some scientific men have forgotten to be astonished. They have come to take it for granted that a complete mathematical description of the world should be possible. This assumption is not a rational one: it is a pure act of faith. The great founders of the scheme made no such mistake: they were quite aware of the precarious nature of their enterprise. Thus, Newton, the greatest and most successful of them all, says that, if they find the mathematical method does not work, they must try a different method. The mathematical method, which is the very essence of modern science, has, however, worked splendidly. From the time of its origination in the seventeenth century until the present day it has had no serious rival. The ancient æsthetic principle, which led to the conclusion that the planets moved in circles because the circle is the only perfect figure, is still used by theosophists, but not by men of science. Similarly the old moralistic principle, which explained the fact of water rising in a pump by saying that nature abhorred a vacuum, possibly lingers on only in such superstitions as that sunlight puts the fire out. In more modern times the only notorious rival of the Newtonian method was the dialectic method of Hegel, who evolved the laws of the universe from his inner consciousness. But the best-known result of this method, that there could not be more planets than were