Such is the outline of his argument. He seems to think that if there be any flaw in it, the only assailable point must be his _extension of the analogy_: "In the chain of analogies which Paley commenced, and which I have continued, I believe there is no defective link. The principle of assailment, if any, is the _extension_ of the analogies beyond the Paley point.... With the extension commences my responsibility. He who proves an irrelevancy in it answers my book." This is, no doubt, a vulnerable point, but we venture to think that it is not the only one. His whole reasoning seems to proceed on an unsound view of the nature and conditions of the argument, and is radically defective in at least _three_ respects. It is not correct to say that the argument of design, is _a mere argument from analogy_. Were it so, it might, like many another process of mere analogical reasoning, yield no more than a probable conclusion or a plausible conjecture. But in the case before us, the conclusion is strictly and properly an _inductive inference_. It may be suggested by the perception of _analogy_, but it is founded on the principle of _causality_. It is capable, therefore, of yielding, not a mere _probability_, but an absolute _certainty_. The fact that analogy is so far concerned in the process cannot weaken a conclusion which rests ultimately on a fundamental law of reason, the ground-principle of all induction. It is true, no doubt, that were we destitute of the conscious possession of intelligence, will, and design, we should be utterly incapable of forming these conceptions, or applying them to the interpretation of Nature; and in a loose sense, it may be said that we are guided by the analogy of our own experience to the belief in an intelligent First Cause; but mere analogy would not produce that belief without the great law of causality, which demands an adequate cause for every effect, nor is this law deprived of its necessary and absolute certainty merely because it comes into action along with, and is stimulated by, the perception of obvious analogies. Is it not equally true, that it is only by our own mental consciousness that we are qualified to conceive of other minds, and that we are, to a certain extent, guided by analogy to the belief that our fellow-men are possessed, like ourselves, of intelligence and design? But who would say that this conclusion is no more than a _probable_ conjecture, or that, depending as it does in part on the analogy of our own experience, it cannot yield absolute certainty? In so far as it is _merely_ analogical, it might be only more or less probable; but being founded also on the law of causality, it is an inductive inference, and, as such, one of the most certain convictions of the human mind.