of the intermediate agency a matter of conjecture, the necessity of some such agency appeared to him indubitable. It would seem that, even now, the majority of scientific men have not completely got over this very difficulty; for though they have at last learned to conceive the sun attracting the earth without any intervening fluid, they cannot yet conceive the sun illuminating the earth without some such medium.
"If, then, it be so natural to the human mind, even in its highest state of culture, to be incapable of conceiving, and on that ground to believe impossible, what is afterwards not only found to be conceivable, but proved to be true; what wonder if, in cases where the association is still older, more confirmed, and more familiar, and in which nothing even occurs to shake our conviction, or even to suggest to us any conception at variance with the association, the acquired incapacity should continue, and be mistaken for a natural incapacity? It is true our experience of the varieties in nature enables us, within certain limits, to conceive other varieties analogous to them. We can conceive the sun or moon falling, for although we never saw them fall, nor ever perhaps imagined them falling, we have seen so many other things fall, that we have innumerable familiar analogies to assist the conception; which, after all, we should probably have some difficulty in framing, were we not well accustomed to see the sun and moon move, (or appear to move,) so that we are only called upon to conceive a slight change in the direction of motion, a circumstance familiar to our experience. But when experience affords no model on which to shape the new conception, how is it possible for us to form it? How, for example, can we imagine an end to space and time? We never saw any object without something beyond it, nor experienced any feeling without something following it. When, therefore, we attempt to conceive the last point of space, we have the idea irresistibly raised of other points beyond it. When we try to imagine the last instant of time, we cannot help conceiving another instant after it. Nor is there any necessity to assume, as is done by the school to which Mr Whewell belongs, a peculiar fundamental law of the mind to account for the feeling of infinity inherent in our conception of space and time; that apparent infinity is sufficiently accounted for by simple and universally acknowledged laws."—Vol. I. p. 313.
Mr Mill does not deny that there exists a distinction, as regards ourselves, between certain truths (namely, that of some, we cannot conceive them to be other than truths,) but he sets no value on this distinction, inasmuch as there is no proof that it has its counterpart in things themselves; the impossibility of a thing being by no means measured by our inability to conceive it. And we may observe, that Mr Whewell, in consistency with the metaphysical doctrine upon space and time which he has borrowed from Kant, ought, under another shape, to entertain a similar doubt as to whether this distinction represent any real distinction in the nature of things. He considers, with Kant, that space is only that form with which the human mind invests things—that it has no other than this merely mental existence—is purely subjective. Presuming, therefore, that the mind is, from its constitution, utterly and for ever unable to conceive the opposite of certain truths, (those, for instance, of geometry;) yet as the existence of space itself is but a subjective truth, it must follow that all other truths relating to it are subjective also. The mind is not conversant with things in themselves, in the truths even of geometry; nor is there any positive objective truth in one department of science more than another. Mr Whewell, therefore, though he advocates this distinction between necessary and contingent truth with a zeal which would seem to imply that something momentous, or of peculiar interest, was connected with it, can advocate it only as a matter of abstract metaphysical science. He cannot participate in that feeling of exaltation and mystery which has led many to expatiate upon a necessary and absolute truth which the Divine Power itself cannot alter, which is equally irresistible, equally binding and compulsory, with God as with man. Of this spirit of philosophical enthusiasm Mr Whewell cannot partake. Space and Time, with all their properties and phenomena, are but recognized as the modes of thought of a human intelligence.
We have marked a number of passages for annotation and extract—a far greater number than we can possibly find place for alluding to. One subject, however, which lies at the very basis of all our science, and which has received a proportionate attention from Mr Mill, must not be amongst those which are passed over. We mean the law of Causation. What should be described as the complete and adequate notion of a cause, we need not say is one of the moot points of philosophy. According to one school of metaphysicians, there is in our notion of cause an element not derived from experience, which, it is confessed on all hands, can teach us only the succession of events. Cause, with them, is that invisible power, that mysterious bond, which this succession does but signify: with other philosophers this succession constitutes the whole of any intelligible notion we have of cause. The latter opinion is that of Mr Mill; at the same time the question is one which lies beyond or beside the scope of his volumes. He is concerned only with phenomena, not with the knowledge (if such there be) of "things in themselves;" that part, therefore, of our idea of cause which, according to all systems of philosophy, is won from experience, and concerns phenomena alone, is sufficient for his purpose. That every event has a cause, that is, a previous and uniformly previous event, and that whatever has happened will, in the like circumstances, happen again—these are the assumptions necessary to science, and these no one will dispute.
Mr Mill has made a happy addition to the usual definition of cause given by that class of metaphysicians to which he himself belongs, and which obviates a plausible objection urged against it by Dr Reid and others. These have argued, that if cause be nothing more than invariable antecedence, then night may be said to be the cause of day, for the one invariably precedes the other. Day does succeed to night, but only on certain conditions—namely, that the sun rise. "The succession," observes Mr Mill, "which is equivalent and synonymous to cause, must be not only invariable but unconditional. We may define, therefore," says our author, "the cause of a phenomenon to be the antecedent, or the concurrence of antecedents, upon which it is invariably and unconditionally consequent."—Vol. I. p. 411.
A dilemma may be raised of this kind. The universality of the law of causation—in other words, the uniform course of nature—is the fundamental principle on which all induction proceeds, the great premise on which all our science is founded. But if this law itself be the result only of experience, itself only a great instance of induction, so long as nature presents cases requiring investigation, where the causes are unknown to us, so long the law itself is imperfectly established. How, then, can this law be a guide and a premiss in the investigations of science, when those investigations are necessary to complete the proof of the law itself? How can this principle accompany and authorise every step we take in science, which itself needs confirmation so long as a process of induction remains to be performed? Or how can this law be established by a series of inductions, in making which it has been taken for granted?
Objections which wear the air of a quibble have often this advantage—they put our knowledge to the test. The obligation to find a complete answer clears up our own conceptions. The observations which Mr Mill makes on this point, we shall quote at length. They are taken from his chapter on the Evidence of the Law of Universal Causation; the views in which are as much distinguished for boldness as for precision.
After having said, that in all the several methods of induction the universality of the law of causation is assumed, he continues:—
"But is this assumption warranted? Doubtless (it may be said) most phenomena are connected as effects with some antecedent or cause—that is, are never produced unless some assignable fact has preceded them; but the very circumstance, that complicated processes of induction are sometimes necessary, shows that cases exist in which this regular order of succession is not apparent to our first and simplest apprehension. If, then, the processes which bring these cases within the same category with the rest, require that we should assume the universality of the very law which they do not at first sight appear to exemplify, is not this a real petitio principii? Can we prove a proposition by an argument which takes it for granted? And, if not so proved, on what evidence does it rest?
"For this difficulty, which I have purposely stated in the strongest terms it would admit of, the school of metaphysicians, who have long predominated in this
