He goes on: “I shall allow, if you please, that the one proposition may justly be inferred from the other; I know in fact that it always is inferred. But if you insist that the inference is made by a chain of reasoning, I desire you to produce that chain of reasoning. The connection between these propositions is not intuitive. There is required a medium which may enable the mind to draw such an inference, if, indeed, it be drawn by reasoning and argument. What the medium is, I must confess, passes my comprehension; and it is incumbent on those to produce it who assert that it exists, and is the origin of all our conclusions concerning matters of fact.” If we regard the matter more closely we may say with certainty: This medium exists not as a substance but as a transition. When I speak in the proposition of “such an object,” I already have “similar” in mind, inasmuch as there is nothing absolutely like anything else, and when I say in the first proposition, “such an object,” I have already passed into the assertion made in the second proposition. Suppose that we take these propositions concretely: (1) I have discovered that bread made of corn has a nourishing effect. (2) I foresee that other apparently similar objects, e.g., wheat, will have a like effect. I could not make various experiments with the same corn in case (1). I could handle corn taken as such from one point of view, or considered as such from another, i.e., I could only experiment with very similar objects. I can therefore make these experiments with corn from progressively remoter starting points, or soils, and finally with corn from Barbary and East Africa, so that there can no longer be any question of identity but only of similarity. And finally I can compare two harvests of corn which have less similarity than certain species of corn and certain species of wheat. I am therefore entitled to speak of identical or similar in the first proposition as much as in the second. One proposition has led into another and the connection between them has been discovered.