tion. And if he asks what kind of induction, the answer cannot be induction in accordance with Mill's Deductive Method, because that presupposes inductions already made in accordance with his Experimental Methods. Nor can it be induction in accordance with these methods, for they presuppose the induction we are now considering. It must be, therefore, induction in accordance with his hypothetical method—our reason for ignoring the position of the stars in our chemical experiments must be that we have made an hypothesis that such circumstances are not material to the result and that our hypothesis explains the facts. The important question is: Are we able to take the second step in induction as Mill conceived it; are we able to show that the hypothesis that the circumstances which chemists consider to be alone possibly material to the result not only explain the facts, but that no other can? Manifestly, to state the question is to answer it. To prove that no other hypothesis except that upon which the science of chemistry rests can explain the facts, is to prove an alibi for the rest of a possibly infinite universe, which is plainly impossible. Any one who will take the pains to grasp the difference that may exist between what is and what is known, will be slow to assert that he has so far made an inventory of all possible existences as to be able to assert that no circumstances except those supposed by chemistry to be possibly material to chemical phenomena can have anything to do with them. Accordingly, if Mill's formula is to describe the facts as they are, it must be rewritten somewhat in this way: "If two or more instances of the phenomenon under investigation have only one circumstance in common among those supposed to be possibly material to the result, the hypothesis that the circumstance in which alone all the instances agree is the cause or effect of the given phenomenon, explains the facts, although we cannot say that to wider knowledge another hypothesis would not equally well explain them." It is unnecessary for my purpose to proceed further with an examination of Mill's theory of induction. Of his Deductive Method and his Hypothetical Method, as well as of his Experimental
