The large and general fact thus stated constitutes, in my opinion, the strongest of all arguments in favour of Mr. Darwin’s theory of natural selection, and therefore we can see the probable reason why it is what it is, so far as the question of its physical causation is concerned.  But where the question is, Supposing the physical causation ultimately due to Mind, what are we to infer concerning the character of the Mind which has adopted this method of causation?—­then we again reach the answer that, so far as we can judge from a conscientious examination of these facts, this Mind does not show that it is of a nature which in man we should call moral.  Of course behind the physical appearances there may be a moral justification, so that from these appearances we are not entitled to say more than that from the fact of its having chosen a method of physical causation leading to these results, it has presented to us the appearance, as before observed, of caring for animal perfection to the exclusion of animal enjoyment, and even to the total disregard of animal suffering.

In conclusion, it is of importance to insist upon a truth which in discussions of this kind is too often disregarded—­viz. that all our reasonings being of a character relative to our knowledge, our inferences are uncertain in a degree proportionate to the extent of our ignorance; and that as with reference to the topics which we have been considering our ignorance is of immeasurable extent, any conclusions that we may have formed are, as Bishop Butler would say, ’infinitely precarious.’  Or, as I have previously presented this formal aspect of the matter while discussing the teleological argument with Professor Asa Gray,—­’I suppose it will be admitted that the validity of an inference depends upon the number, the importance, and the definiteness of the things or ratios known, as compared with the number, importance, and definiteness of the things or ratios unknown, but inferred.  If so, we should be logically cautious in drawing inferences from the natural to the supernatural:  for although we have the entire sphere of experience from which to draw an inference, we are unable to gauge the probability of the inference when drawn—­the unknown ratios being confessedly of unknown number, importance, and degree of definiteness:  the whole orbit of human knowledge is insufficient to obtain a parallax whereby to institute the required measurements or to determine the proportion between the terms known and the terms unknown.  Otherwise phrased, we may say—­as our knowledge of a part is to our knowledge of a whole, so is our inference from that part to the reality of that whole.  Who, therefore, can say, even upon the hypothesis of Theism, that our inferences or “idea of design” would have any meaning if applied to the “All-Upholder,” whose thoughts are not as our thoughts?’[30] And of course, mutatis mutandis, the same remarks apply to all inferences having a negative tendency.