Science, and especially the theory of evolution, has enormously extended our inferential experience, but it has done so only by accepting the common faith that experience may be trusted, that is to say, that the environment, the cosmos, is trustworthy within our experience of it. When, then, the optimist alleges that the process of evolution has been, on the whole, a course of progress, he is but showing that the common faith in the trustworthiness of the reality in which we move and have our being justifies itself. But he does not show us, nor does science show us, why the real, the cosmos, is trustworthy: he ends by showing that it is trustworthy because he began, like all of us, by trusting it. He is quite right: it is the only way in which to demonstrate that either science, or morality, or religion is trustworthy--by giving our faith, to start with. Only when we are satisfied as to the fact can we profitably inquire the reason; and the reason is to be found only in the nature of the real, as revealed to us in the sum total of our experience, scientific, moral, and religious. But the will to believe that experience and to trust the real which it reveals, is free: if a man will not accept it as trustworthy, there is for him no reason why. The case is different with the man who does accept the testimony of consciousness as evidence of the reality to which it testifies. For him the one reality is Will, and the ideals of science, morality, and religion are the expressions of that Will. In accepting them as the principles of thought and action he does not learn what is the purpose of evolution, the final cause of the cosmos: he chooses to believe that, by so accepting them and by striving to realise the ideal, he is fulfilling the Divine Will and contributing his share to the realisation of the rational purpose to which, he assumes, the process of evolution is tending. But in so doing he does not renounce his freedom: his resolution to believe is an exercise of his free will, an act, "a great act," of faith. If carried into effect in his daily life, his resolution, daily renewed and ever free, may in the end become a daily act of love, and then he will understand the reason why the cosmos, or the cosmic power, is trustworthy. Only love of man could have given man, as his ideals, to know the truth and do the right. Only if man's ideals are so given is the cosmos trustworthy--if it is trustworthy. If it is not, then there is no truth to know, no right to do, no inference can be drawn from the past to the future, for the past, even of a minute ago, may be a delusion.