To Mr. Francis E. Abbot.

Cambridge, Dec. 20, 1864.

I received a few days ago your essay on the Unconditioned from the “North American Review,” with your request for thoughtful criticisms of the views presented therein.

I am greatly obliged to you for this favor and gratified by your invitation. Your essay has pleased me much by its beautiful philosophical style and admirable clearness, and it seems to me to evince very great metaphysical ability. I have not, however, given that studious attention to it which will warrant me in undertaking an elaborate defence of Hamilton’s doctrine against your strictures, or in attempting more than an indication of the objections to them which I felt rather than clearly excogitated in a cursory reading. Indeed, I should now hesitate to say any thing, but for my desire, in acknowledging your favor, to comply as far as possible with your request, and because I shall not be better prepared, for a long time to come.

Your doctrine is founded on the position of a distinct faculty of knowledge, — the supersensuous reason, — which Hamilton, so far from having overlooked, expressly rejects, as not warranted

by an analysis of the mind and its contents; and the difference between his doctrine and that of all his opponents rests ultimately in their psychological analyses.

In order to establish his exclusion of reason as a faculty of knowledge, or as any thing more than the sum of the necessary limits and conditions of knowledge, it behooved him to account for the fact of a belief in unconditioned existence, and to show how a belief is possible without a knowledge, either intuitive or inferential. He was opposed to the rationalists, on the one hand, by denying that the negative proposition, “There are no limits,” or the equally negative proposition, “The limits are absolute or unconditional,” — can be either proved or positively made known by intuition. He differed from the empiricists, on the other hand, by not overlooking or rejecting the fact of a belief in the unconditioned in general, or the fact that unexperienced and unprovable negative propositions may yet have valid claims on our credence. The positive part of his doctrine maintains against empiricism that such a belief is valid, and the critical part examines the explanations of this validity given by the rationalists; and he rejects even Kant’s quasi faculty of reason or regulative faculty, as assumed simply for the sake of this explanation and as being unnecessary to it.

It seems to me, therefore, that the justness of your criticism of Hamilton turns on the correctness of your preceding psychological analysis of Space and Time as rational ideas, in which you assume a faculty capable of attributing to these relations the negative notions of infinity and incomposite unity.

The existence of such a faculty is the only real question between you and Hamilton, and you yourself allow that the validity of a part of your criticism rests on the accuracy of your analysis of Space as necessarily illimitable. I ought to notice here, in passing, that Hamilton uses Space and Time as illustrative examples of the attribution of the negative

notions “infinite” and “absolute,” and not to defend any doctrine about space and time as metaphysical objects. He says in his letter to Mr. Calderwood, “that there is a fundamental difference between The Infinite (τ ὸ ἓ ν κ α ι π ᾶ ν), and a relation to which we may apply the term infinite. Thus, Time and Space must be excluded from the supposed notion of The Infinite; for The Infinite, if positively thought it could be, must be thought as under neither Space nor Time.” I am especially desirous to call your attention to this point in Hamilton’s very interesting letter, because it agrees with your own conclusions on the danger of reasoning from quantitative infinity. But Hamilton does not so reason, as you seem to suppose.

Space and Time only enter as essential elements into the discussion through your analysis of them. And if the negative notion “infinity” be derivable, as you maintain, from a positive faculty of knowledge competent to vouch for the proposition, “There are no limits to space or time,” then these ideas, as the source of the notions, may become essential to the discussion, and Hamilton’s illustrations may be shown to be absurd. But the discussion really goes back of this, and tests the correctness of such a psychological analysis.

Again, before coming directly to this discussion, I must notice, with reference to your analysis, that Hamilton himself insists upon a distinction between Space and Extension, which, however, is different from yours, and he proposes the names Extension and Space to designate the two notions, which are, as he supposes, derived from two sources; namely, the primary intuitions of sense, in virtue of which we actually and immediately apprehend the extension of objects, and the intellectual form of Space through which we are necessitated to conceive of every thing as in relation to extension; but this form is not in Hamilton’s Philosophy an object of thought. It is a determinant, but not a constituent of knowledge.

Indeed, a Form, in Kantian phraseology, is neither a knowledge nor a faculty of knowledge, but rather a determinant of the limits of knowledge, though regarded by Kant himself as something more than a negation of knowledge.

While you denote by Extension the same thing that Hamilton proposes to designate by that name, your Space, as a positive datum of a distinct faculty, the supersensuous reason, is different from, and even a contradiction of what Hamilton proposes to call by that name, or that which compels us to think always in relation to extension. That which you call Space seems to me to coincide in part with the empiricist’s abstract space, or the mere notion, which like any other general notion is supersensuous or unimaginable, simply because imagination or representation is always of the particular possible in experience. But you pass beyond the empiricist’s abstract space, when you assume a faculty competent to connect the notions of space and infinity, and to vouch for the truth of the proposition that “Space is infinite;” and in fact you thus assume the real point at issue.

I do not propose to undertake a counter analysis, but shall limit myself to pointing out Hamilton’s exposition of the meaning of the judgment “Space is infinite,” — a judgment for which you have, with the rationalists, felt obliged to assume a supersensuous positive faculty of knowledge. It is really a statement somewhat elliptical of the fact that space extends beyond our power of knowing or conceiving it. The statement involves the subjective fact that the all of space is incognizable and inconceivable by us, though this fact is expressed in an objective form, as if this inconceivability were a property of the object itself. The abstractive power of the understanding cannot aid us, for this adds nothing to our knowledge. Disregarding the picture, then, and thinking no longer of that colored expansion, the sky, we do not come to any object in our experience of which we can positively think that it is infinite.

All that we can positively think of the abstractest conception of Space is, that we are unable to conceive it at the same time as the abstractest and as definitely bounded. But this is neither thinking nor implying that space in itself is unlimited, much less does it imply a knowledge that Space is unlimited; and Hamilton not only denies the possibility of such a knowledge, but denies that we can even conceive the possibility of such a knowledge. “Space is limited;” “Space is unlimited,” — these propositions, so far as they express any thing which is actually in the mind, are each the recoil of thought from the other, and we finally rest on unlimited space as the least obtrusive and staggering inconceivability, and the one for which we can most easily substitute a pseud representation, — namely, an indefinitely great extension. But this negative proposition is not only insusceptible of proof or of intuition: the synthesis of its terms is impossible in thought, or, as Hamilton says, is inconceivable.

This leads me to speak of Hamilton’s use of the words “conception” and “conceivability,” which, I think, you have misapprehended. If there be any term in the vocabulary of Philosophy which our author is especially anxious to use in a single, unambiguous sense, it is the word “conception,” which he alone among British philosophers used, throughout his writings, as the name of the act of the understanding or of the elaborative faculty, though sometimes it stands for the product (more properly concept) of this faculty. He never uses the word as synonymous with imagination, or to denote an act of imagination, except where, as in the present discussion, the act of the two faculties coincide. To understand or conceive a house on fire, and to imagine or picture it, are essentially the same act, but the terms direct attention to different aspects of this act, and this difference becomes an essential one, when we consider abstract and general terms applicable equally to many objects; for here the particularity of the acts of sensuous

imagination makes them inadequate to determine the sense of a general term, which may, nevertheless, be understood or conceived; and it is only in this meaning of the word “conception,” and in the cognate senses of the derivative terms, that Hamilton ever employs them. Infinite Space, if it be an object of thought at all, is a single particular object; and hence, if it cannot be imagined, it cannot be conceived. Hamilton also points out, what is quite as essential to this discussion, another ambiguity in the use of this word, which he himself carefully avoids, and of which he convicts Dr. Reid. It is generally incorrect to speak of imagining a proposition, as you seem to accuse Hamilton of doing, but even when we speak of conceiving a proposition we are not out of danger; for Dr. Reid says that he can conceive of the proposition that two sides of a triangle are together less than the third side, though the proposition is absurd, and hence he concludes that the possibility of conceiving is not a test of truths. But Hamilton points out the fact that conceiving the terms of a proposition and the logical form by which they are bound together is not conceiving the proposition itself, which he renders, in order to avoid this ambiguity, by the phrase, “conceiving the possibility of the propositions.” If the proposition is not a general truth, this is the same as imagining, or representing in the phantasy, the synthesis of its terms. We must not suppose even in case of a possibly true proposition, of which neither proof nor intuition is possible, that the supposition of its truth, and an understanding of its terms and its logical form, constitute any thing more than what philosophers call a symbolical conception; which, indeed, is no conception at all.

The propositions in question in the present discussion are not general truths, but particular ones; and if imagining and conceiving are the only kinds of thinking, these propositions cannot be thought. We should not regard that as cogitable of which we only have symbolical conceptions, since we have

symbolical conceptions of absurdities. The supersensuous reason as a faculty of thought and knowledge is an invention of the rationalists to account for the belief we have in an unconditional, unimaginable reality; but this invention Hamilton regards as unnecessary, and therefore unwarranted. The laws of thought are alone sufficient, he thinks, to account for this belief. For if it is possible to frame concerning any nature two propositions in each of which there is no incongruity of terms, but which contradict each other, then, since one must be true, we have evidence of the existence of this nature in the laws of thought themselves. We have no means of knowing which of two mutually exclusive inconditionates is the truth, but we have evidence that something inconceivable is true, and therefore “that the capacity of thought is not to be constituted into the measure of existence.” This is the gist of Hamilton’s arguments; and it is opposed equally to the scepticism which would limit faith to the domain of real knowledge, and to the dogmatism which would extend knowledge to the horizon of a legitimate faith.

Herbert Spencer has totally misconceived the purport of the reasoning, and he supposes Hamilton to have argued in the interest of empiricism. Mr. Mansel, on the other hand, has sought to shield ecclesiastical authority from the assaults of rational criticism, and, by a wholly gratuitous application of Hamilton’s doctrines, to place absurd and meaningless dogmas in the same category with inconceivable reality. This of course begs the question; and indeed any positive doctrine of faith begs the question, is incapable of proof. The test of a true faith is emotional and moral, not intellectual. Our respects must decide what is worthy of belief. Not what claims our respect, but what gains it, is our true faith, and the basis of our religion; and nobility of character is the sole end and criterion of its validity.

Your treatment of Hamilton’s definition of the conditioned

as “a mean between two extremes, two inconditionates, &c.,” seems to me to be a little captious. He of course does not regard it as a logical mean, else, as you say, the law of excluded middle would not apply. The expression is obviously metaphorical, or perhaps we may say he uses the word in a psychological sense, to denote the only effective effort to conceive, in which the mind rests from efforts ineffective in directions logically opposed to each other; but we must distinguish between the logical opposition of these supposed objects of knowledge and the mental acts by which we attempt, but without success, to comprehend them. These acts are still of the conditioned; and, being inept and irrelevant, they are in a sense opposed to both the logical extremes, which they fail to comprehend.

According to this interpretation, which has always seemed to me to be Hamilton’s meaning, your diagram of oppositions, which is simply logical, is quite misplaced. The first part of Hamilton’s paragraph, ending in the italicized words “can be conceived as possible,” is the statement of the psychological difficulty. The last part, ending in the italics, “must be admitted as necessary” is the solution, — the only solution which the laws of thought can give of this difficulty. It is not a real solution. The difficulty is not removed, but it is reconciled with a belief in unconditioned existence. At least, Hamilton and his followers believe it to be so reconciled; and this is the purport of his philosophy, which, so far from being a defence of empiricism, is a defence of faith against empiricism, — not by denying incontrovertible facts on the one hand, the limitations of sense and understanding; nor yet by assuming an indefensible dogma on the other hand, the position of a faculty of absolute knowledge; but by showing how the limits of thought may disclose themselves as such, or prove that thought is limited not simply by ignorance and inexperience, but by the conditions of its positive activity.

Hamilton’s list of “Contradictions Proving the Psychological Theory of the Conditioned,” which he gives without comment, was given, I suppose, to illustrate by a wider induction the absurdity of attributing infinity to any thing cognizable; and your comments only carry out the obvious intent of the author. You explain the absurdities by showing that the notion of infinity is inapplicable to the several cases supposed, and so far you agree with Hamilton; but he would go farther, and regard these examples as affording inductive proof that the notion of infinity is inapplicable to any thing conceivable.

I regret that this restatement of such portions of Hamilton’s doctrine of the conditioned as seemed to me, after reading your valuable criticism, to require elucidation and emphasis, is all that I can do in answer to your request. A more detailed examination would have required a more careful reading of your essay than I have had time to give it.