"But it may be said, that we do learn, by means of observation and experience, many universal truths; indeed, all the general truths of which science consists. Is not the doctrine of universal gravitation learned by experience? Are not the laws of motion, the properties of light, the general properties of chemistry, so learned? How, with these examples before us, can we say that experience teaches no universal truths?

"To this we reply, that these truths can only be known to be general, not universal, if they depend upon experience alone. Experience cannot bestow that universality which she herself cannot have, and that necessity of which she has no comprehension. If these doctrines are universally true, this universality flows from the ideas which we apply to our experience, and which are, as we have seen, the real sources of necessary truth. How far these ideas can communicate their universality and necessity to the results of experience, it will hereafter be our business to consider. It will then appear, that when the mind collects from observation truths of a wide and comprehensive kind, which approach to the simplicity and universality of the truths of pure science; she gives them this character by throwing upon them the light of her own fundamental ideas."—Whewell, Vol. I. p. 60.

Accordingly, Mr Whewell no sooner arrives at any truth which admits of an unconditional positive statement—a statement defying all rational contradiction—than he abstracts it from amongst the acquisitions of experience, and throwing over it, we suppose, the light of these fundamental ideas, pronounces it enrolled in the higher class of universal and necessary truths. The first laws of motion, though established through great difficulties against the most obstinate preconceptions, and by the aid of repeated experiments, are, when surveyed in their present perfect form, proclaimed to be, not acquisitions of experience, but truths emanating from a higher and more mysterious origin.²

This distinction, which assigns a different mental origin to truths, simply because (from the nature of the subject-matter, as it seems to us) there is a difference with regard to the sort of certainty we feel of them, has always appeared to us most unphilosophical. It is admitted that we arrive at a general proposition through experience; there is no room, therefore, for quibbling as to the meaning of the term experience—it is understood that when we speak of a truth being derived from experience, we imply the usual exercise of our mental faculties; it is the step from a general to a universal proposition which alone occasions this perplexing distinction. The dogma is this—that experience can only teach us by a limited number of examples, and therefore can never establish a universal proposition. But if all experience is in favour of a proposition—if no experience has occurred even to enable the imagination to conceive its opposite, what more can be required to convert the general into a universal proposition?

Strange to say, the attribution of these characteristics of universality and necessity, becomes, amongst those who loudly insist upon the palpable nature of the distinction we are now examining, a matter of controversy; and there are a class of scientific truths, of which it is debated whether they are contingent or necessary. The only test that they belong to the latter order is, the impossibility of conceiving their opposites to be the truth; and it seems that men find a great difference in their powers of conception, and that what is impossible with one is possible with another. But (wisely, too) passing this over, and admitting that there is a distinction (though a very ill-defined one) between the several truths we entertain of this nature; namely, that some we find it impossible, even in imagination, to contradict, whilst of others we can suppose it possible that they should cease to be truths—does it follow that different faculties of the mind are engaged in the acquisition of them? Does nothing depend on the nature of the subject itself? "That two sides of a triangle," says Mr Whewell, "are greater than the third, is a universal and necessary geometrical truth; it is true of all triangles; it is true in such a way that the contrary cannot be conceived. Experience could not prove such a proposition." Experience is allowed to prove it of this or that triangle, but not as an inseparable property of a triangle. We are at a loss to perceive why the same faculties of the mind that can judge, say of the properties of animal life, of organized beings, cannot judge of the properties of a figure—properties which must immediately be conceived to exist the moment the figure is presented to the imagination. We say, for instance, of any animal, not because it is this or that animal, a sheep or an ox, but simply as animal, that it must sustain itself by food, by the process of assimilation. This, however, is merely a contingent truth, because it is in our power to conceive of organized beings whose substance shall not wear away, and consequently shall not need perpetual restoration. But what faculty of the mind is unemployed here that is engaged in perceiving the property of a triangle, that as triangle, it must have two sides greater than the third? The truths elicited in the two cases have a difference, inasmuch as a triangle differs from an animal in this, that it is impossible to conceive other triangles than those to which your truth is applicable, and therefore the proposition relating to the triangle is called a necessary truth. But surely this difference lies in the subject-matter, not in the nature of our mental faculties.

But we had not intended to interpose our own lucubrations in the place of those of Mr Mill.

"Although Mr Whewell," says our author, "has naturally and properly employed a variety of phrases to bring his meaning more forcibly home, he will, I presume, allow that they are all equivalent; and that what he means by a necessary truth, would be sufficiently defined, a proposition the negation of which is not only false, but inconceivable. I am unable to find in any of Mr Whewell's expressions, turn them what way you will, a meaning beyond this, and I do not believe he would contend that they mean any thing more.

"This, therefore, is the principle asserted: that propositions, the negation of which is inconceivable, or in other words, which we cannot figure to ourselves as being false, must rest upon evidence of higher and more cogent description than any which experience can afford. And we have next to consider whether there is any ground for this assertion.

"Now, I cannot but wonder that so much stress should be laid upon the circumstance of inconceivableness, when there is such ample experience to show that our capacity or incapacity for conceiving a thing has very little to do with the possibility of the thing in itself; but is in truth very much an affair of accident, and depends upon the past habits and history of our own minds. There is no more generally acknowledged fact in human nature, than the extreme difficulty at first felt in conceiving any thing as possible, which is in contradiction to long-established and familiar experience, or even to old and familiar habits of thought. And this difficulty is a necessary result of the fundamental laws of the human mind. When we have often seen and thought of two things together, and have never, in any one instance, either seen or thought of them separately, there is by the primary law of association an increasing difficulty, which in the end becomes insuperable, of conceiving the two things apart. This is most of all conspicuous in uneducated persons, who are, in general, utterly unable to separate any two ideas which have once become firmly associated in their minds, and, if persons of cultivated intellect have any advantage on the point, it is only because, having seen and heard and read more, and being more accustomed to exercise their imagination, they have experienced their sensations and thoughts in more varied combinations, and have been prevented from forming many of these inseparable associations. But this advantage has necessarily its limits. The man of the most practised intellect is not exempt from the universal laws of our conceptive faculty. If daily habit presents to him for a long period two facts in combination, and if he is not led, during that period, either by accident or intention, to think of them apart, he will in time become incapable of doing so, even by the strongest effort; and the supposition, that the two facts can be separated in nature, will at last present itself to his mind with all the characters of an inconceivable phenomenon. There are remarkable instances of this in the history of science; instances in which the wisest men rejected as impossible, because inconceivable, things which their posterity, by earlier practice, and longer perseverance in the attempt, found it quite easy to conceive, and which every body now knows to be true. There was a time when men of the most cultivated intellects, and the most emancipated from the dominion of early prejudice, could not credit the existence of antipodes; were unable to conceive, in opposition to old association, the force of gravity acting upwards instead of downwards. The Cartesians long rejected the Newtonian doctrine of the gravitation of all bodies towards one another, on the faith of a general proposition, the reverse of which seemed to them to be inconceivable—the proposition, that a body cannot act where it is not. All the cumbrous machinery of imaginary vortices, assumed without the smallest particle of evidence, appeared to these philosophers a more rational mode of explaining the heavenly motions, than one which involved what appeared to them so great an absurdity. And they, no doubt, found it as impossible to conceive that a body should act upon the earth at the distance of the sun or moon, as we find it to conceive an end to space or time, or two straight lines inclosing a space. Newton himself had not been able to realize the conception, or we should not have had his hypothesis of a subtle ether, the occult cause of gravitation; and his writings prove, that although he deemed the particular nature 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.