he treats of the properties of the spheres, he does not clearly show the causal relation, nor does he explain the phenomena in that systematic way which the hypothesis of natural laws would demand. For let us consider the spheres: in one case a sphere with greater velocity is above a sphere with less velocity, in another case we notice the reverse; in a third case there are two spheres with equal velocities, one above the other. There are, besides, other phenomena which speak strongly against the hypothesis that all is regulated by the laws of Nature, and I will devote a special chapter to the discussion of these phenomena. In short, there is no doubt that Aristotle knew the weakness of his arguments in tracing and describing the cause of all these things, and therefore he prefaces his researches on these things as follows:—“We will now thoroughly investigate two problems, which it is our proper duty to investigate and to discuss according to our capacity, wisdom, and opinion. This our attempt must not be attributed to presumption and pride, but to our extraordinary zeal in the study of philosophy; when we attempt the highest and grandest problems, and endeavour to offer some proper solution, every one that hears it should rejoice and be pleased.” So far Aristotle. This shows that he undoubtedly knew the weakness of his theory. How much weaker must it appear when we bear in mind that the science of Astronomy was not yet fully developed, and that in the days of Aristotle the motions of the spheres were not known so well as they are at present. I think that it was the object of Aristotle in attributing in his Metaphysics one Intelligence to every sphere, to assume the existence of something capable of determining the peculiar course of each sphere. Later on I will show that he has not gained anything thereby; but now I will explain the words, “according to our capacity, wisdom, and opinion,” occurring in the passage which we quoted. I have not noticed that any of the commentators explain them. The term “our opinion” refers to the principle that everything is the result of natural laws, or to the theory of the Eternity of the Universe. By “our wisdom” he meant the knowledge of that which is clear and generally accepted, viz., that the existence of every one of these things is due to a certain cause, and not to chance. By “our capacity” he meant the insufficiency of our intellect to find the causes of all these things. He only intended to trace the causes for a few of them; and so he did. For he gives an excellent reason why the sphere of the fixed stars moves slowly, while the other spheres move with greater velocity, namely, because its motion is in a different direction [from the uppermost sphere]. He further says that the more distant a sphere is from the eighth sphere the greater is its velocity. But this rule does not hold good in all cases, as I have already explained (p. 174). More forcible still is the