The only conceivable answer to the question, "What is that which is now a mollusc and now a man and now an inorganic atom?"[32] is given by man himself--and his answer is, I fear, not "scientific." It is "I Am." "I am that which varies." And the force of his answer depends on what he means by the word "I." And so also the only conceivable answer to the absolute datum question is to be found in the meaning of the word "I"--in the deepening back of consciousness itself. Man is the measure of all things. If we are to use Science as a minister to the most external part of man--to provide him with cheap boots and shoes, etc.--then we do right to seek our absolute datum in his external part, and to take his _foot_ as our first measure. We found a science on feet and pounds, and it serves its purpose well enough. But if we want to find a garment for his inner being--or, rather, one that shall fit the _whole_ man--to wear which will be a delight to him and, as it were, a very interpretation of himself--it seems obvious that we must not take our measure from outside, but from his very most central principle. The whole question is, whether there _is_ any absolute datum in this direction or not. There have been men through all ages of history (and from before) who have declared that there is. They have perhaps been conscious of it in themselves. On the other hand there have been men who, starting from their feet, declared that consciousness itself was a mere incident of the human machine--as the whistle of the engine--and thus the matter stands. On the whole, at the present day, the _feet_ have it, and (notwithstanding their variety in size and boot-induced conformation) are generally accepted as the best absolute datum available.