Review of Mill on Hamilton [From North American Review 103.2 (July 1866): 250-260.] ²⁸

An Examination of Sir William Hamilton's Philosophy, and of the principal Philosophical Questions discussed in his Writings. By John Stuart Mill. Boston: William V. Spencer. 1865. 2 vols. 12mo. pp. 330 and 354.

The value of this most searching examination of Sir William Hamilton’s writings, and its enduring interest as a contribution to philosophy, separating it widely from the short-lived publications of the season, are sufficient apologies for calling our readers’ attention to it at this late day. In one respect, indeed, the work is a very timely publication, and in this it exhibits a literary skill of no ordinary merit. The position and present reputation both of the author and his subject are such, that the mere announcement of the work was sufficient to inspire with the liveliest curiosity every student of philosophy.

The writings of Sir William Hamilton have been so long published, that they have had a fair chance to gain a hearing, and to gain such prepossession of thinking minds, that their critic was sure of an intelligent and deeply interested attention, if not of an unprejudiced one; and his criticisms are the more effective, since they are not obliged to inform the

reader for the first time of the issues in question. They fall upon very widely known and popular opinions, which the influence of Sir William Hamilton has organized into a school of considerable extent, both in Great Britain and America. The recent prominent position of Mr. Mill in the political world has doubtless drawn the attention of many to this work who were not acquainted with his previous philosophical writings and his position among British philosophers.

Barely in the history of philosophy has so excellent an opportunity been so judiciously used. What will interest the reader most is, in fact, only incidental to the main object of the work, which is to define and justify the opinions of the school of philosophy usually accounted unorthodox, of which Mr. Mill is the principal adherent among living English thinkers. He has taken this occasion to develop his views on several fundamental questions in philosophy, which have only appeared incidentally in his previous works. “My subject,” he says, “is not Sir William Hamilton, but the questions which Sir William Hamilton discussed.” The reader will, however, retain most vividly the impression that the work is a masterly polemic against the opinions and the influence of the man whose acknowledged abilities as a teacher of philosophy have produced an erroneous impression of his powers as a thinker. In this his critic has wisely pursued a policy which is a secret of success in all controversies, as well in philosophy as in practical politics, — the policy of taking the offensive. On the critic’s success in discrediting an acknowledged authority in philosophy rest, in great measure, the chances of his own opinions to gain a hearing; and they have the additional chance in such a mode of presentation, by challenging comparison, to gain a fair hearing.

Such a course was the more desirable, because the philosophy of Sir William Hamilton, while it retains most of the positions essential to orthodoxy, appears to adopt from the opponents of his school their strong points, and to reconcile them with the authorized religious or orthodox philosophy. The principal doctrine which Sir William Hamilton thus seems to adopt from his opponents is the doctrine of the relativity of human knowledge. This doctrine teaches that knowledge, even in its highest exercise, is only a cognizance of states of the mind, and that our faculties can recognize these only as effects on us, produced, we know not how, by powers we know not what, — that any other natures than such mental states cannot be cognized at all, or recognized as other than the unknowable, which we may suppose to exist, but cannot suppose to be in any manner comprehensible. Idealism and sensationalism both postulate this doctrine; and Sir William Hamilton, apparently adopting it also, attempts nevertheless to refute these philosophies. This at least appears to be the main issue of Mr. Mill’s criticism.

It is certain that Hamilton adopts this doctrine to the extent of affirming that the known implies a something unknown, which is necessarily supposed as the ground of its reality, or as the unknown cause of the objects of knowledge; and he calls the knowable phenomenon an effect. The real difference between him and his critic appears to us to be, that, while both recognize the coexistence of a something known and a something unknown in every act of real knowledge, Mr. Mill, with the idealists, identifies this antithesis with the distinction of the ego and non-ego, the known effect being with him an effect on us by an unknown cause in the non-ego; while Hamilton does not regard the two distinctions as coextensive. That things in themselves as absolutely and necessarily existing or as uncaused cannot be known to us, is what we understand to be Hamilton’s doctrine of the relativity of knowledge; but this does not signify, with him, that the objects of knowledge are effects on us. On the contrary, he regards the evidence of our immediate cognizance of a non-ego to be quite independent of this doctrine, and by no means inconsistent with it. With Hamilton, the relativity of knowledge does not decide the fact of an immediate knowledge of a non-ego in a phenomenal external world, but only determines the character of this knowledge, as a phenomenal one, relatively, not to the ego, but to the real existence of the external world itself.

The difference between Hamilton and Mr. Mill may be reduced, we conceive, to a difference in the meanings they attach to the word “phenomenon.” With Hamilton it has an extended meaning; so that the phenomenal scarcely signifies more than that existence which necessarily implies some other, of which it is the manifestation, — some hidden existence necessarily inferred, though in itself unknown. But with Mr. Mill the word seems to signify more specifically a mental state, implying some cause which is not a mental state. The doctrine that all knowledge is only of phenomena will of course admit of two different interpretations, according to these two meanings of the word. With Mr. Mill’s or the idealist’s meaning of the word, it follows that an immediate knowledge of a non-ego is impossible. But if Hamilton’s more extended use of the word be admissible, then an existence non-ego may be immediately cognizable consistently with the doctrine of the relativity of knowledge, provided this non-ego be phenomenal, that is, necessarily dependent on some other incognizable existence among the real causes of things. Whether Mr. Mill has failed to discover the precise significance of Hamilton’s use of this word, or, regarding it as inadmissible, has chosen to hold him to the authentic meaning, does not appear. If the latter was the case, we conceive that the criticism might have been made more to the point. Mr. Mill takes issue, however, on what he conceives

to be an inconsistency between two portions of Hamilton’s writings, —bis theory of the perception of the primary qualities of matter in his notes to Reid, and his doctrine of the relativity of knowledge in his Lectures. This is the chief issue of the book; but if the meaning of the word “phenomenon” which we have attributed to Hamilton be a valid one, his philosophy escapes from this criticism by affirming that the primary qualities of matter, that is, the having extension, figure, etc., though not cognized as the effects of matter on us, are yet modes of existence implying an unknown substance, and are hence phenomenal in Hamilton’s meaning of the word.

We think it would have been proper enough to object to Hamilton’s description of these qualities as effects, in any other sense than as effects on us, — a description which confounds effects with attributes; but instead of discovering this confusion, Mr. Mill supposes that Hamilton meant to represent the primary qualities of matter as effects on us, while he inconsistently ascribed to them an existence independently of us. In the criticism on Hamilton’s theory of causation, Mr. Mill does indeed discover a confusion corresponding to this, but he misinterprets it. In this theory Hamilton confounds cause with substance, in a manner analogous to his confounding effects with qualities; but while Mr. Mill has clearly pointed out the fact of this confusion, he has failed, we think, to discover its significance or its origin in the point of view of Hamilton’s philosophy. Just as Hamilton extended the application of the word “phenomenon” beyond its use by the idealists, so did he with as little warning extend the word “cause” to denote, not merely one of the essential elements of an event, but also to mean any existence, whether known or unknown, without which neither a quality nor an event could be manifested. With Hamilton a cause signified more than the necessary antecedent of an event. It meant that which makes an antecedent necessary, and without which qualities neither appear nor change. While he denied that a cause in this sense could in itself be known, he maintained that, as implied in all phenomena, it is known as the unchangeable determinant of all changes, and as persisting through change and under all phenomena. The metaphorical phrases and the illustrations by which Hamilton set forth this view of causation, representing the constancy of cause by the law that an effect is equal to the sum of its causes, and that the sum of real existences in causation remains unchanged, are so far misinterpreted by Mr. Mill that he supposes not merely that Hamilton confounded cause with substance, but also the efficient cause with the material, or the cause of changes with the substance which is changed. On the contrary, Hamilton is far from confounding the existence which determines with that which is determined,

or the invariable attributes of the latter with the immutable substance of the former, or the physical law of the indestructibility of matter with the metaphysical law of immutable causes, — as Mr. Mill appears to think.

Perhaps in this case also Mr. Mill has chosen rather to hold his author to what he conceives to be an authentic use of terms, than to try to discover the consistent though metaphysical significations in which Hamilton used them. At any rate, in following the course he did, he has made Hamilton appear sufficiently contradictory and absurd, as if his aim were, as we have intimated, rather to discredit the authority of his author than to ascertain and criticise his real doctrines. Thus Mr. Mill says that,

“According to Sir William Hamilton, when we say that everything must have a cause, we mean that nothing begins to exist, but everything has always existed. I ask any one, either philosopher or common man, whether he does not mean the exact reverse; whether it is not because things do begin to exist, that a cause must be supposed for their existence. The very words in which the axiom of causation is commonly stated, and which our author in the first words of his exposition adopts, are, that everything which begins to exist must have a cause. Is it possible that this axiom can be grounded on the fact that we never suppose anything to begin to exist? Does not he who takes away a beginning of existence take away all causation and all need of a cause? Sir William Hamilton entirely mistakes what it is which causation is called in to explain.”

We think, rather, that Mr. Mill has entirely mistaken what it is that Sir William Hamilton calls in for this explanation. His problem was to explain the beginnings, the persistence, and the endings of things as phenomena, or as they are known to us, and in their relations in their orders of necessary sequence. This Sir William Hamilton proposes to explain by the doctrine that things, not as phenomena, but in themselves and in their real existence, do not change; and he grounds this doctrine on his law of the conditioned, the really central and characteristic position of his philosophy. With this law, and not by its own merits, must Hamilton’s doctrine of causation stand or fall. The unsoundness of this law, which Mr. Mill has sufficiently exposed, is in postulating judgments concerning what, by their very nature, cannot be the subjects of judgments, namely, things in themselves. But this will appear more clearly in what follows.

Mr. Mill’s criticism of Hamilton’s law of the conditioned, and of the methods followed by Hamilton and his school, are by far the most effective portions of the work. Kant had taught concerning things in themselves, that their existence in an intelligible world and the possibility

of an intuition of them as noumena, that is, independently of sensuous perception, could be held only as problematical. Such a possibility of knowledge could neither be asserted nor denied from the conditions of possible experience, and neither proved nor disproved from the data of intuition. Sir William Hamilton, holding substantially the same view of a knowledge of the absolute, but rejecting Kant’s analysis of the conditions of experience, and his ideal affirmation of ontological beliefs, attempts by a profounder classification of possible realities to prove, while refuting the positions of the absolutists, that we may legitimately hold for true what we can neither conceive as possible nor know by intuition; for logic itself compels us, he thinks, to assert one of two contradictory propositions, and to deny the other, concerning things in themselves, each of which alone might be merely problematical. Hence he held that there are possibilities, neither proved by the capacities of thought nor by those of intuition, which can yet be held for true. These he called the Unconditioned. Those possibilities which experience and its conditions determine he called the Conditioned. The laws of logic, disclosing the limits of the conditioned, make known, according to Hamilton, the existence of the unconditioned, or that of which the possibility cannot be conceived. But how does logic disclose these limits? By showing that of two contradictories, neither of which is contained within the conditioned or the thinkable, one must be true, and hence that truth transcends the thinkable.

Mr. Mill elsewhere, and on wholly different grounds, also rejects conceivability as a test of possibility, and so far agrees with his author. He was, therefore, concerned only with this point of difference, namely, Hamilton’s doctrine that, while truth may transcend the thinkable, belief may transcend it also. This he refutes, by showing that there is no validity in applying the laws of logic except to the thinkable. To the Unconditioned — to things in themselves — the laws of logic cannot be presumed to be applicable. Of phenomenal existences, it is true, the laws of logic cannot be denied; but the antinomies on which Hamilton’s doctrine of the Conditioned is founded are propositions about things in themselves, or else they are propositions which are not really inconceivable. Infinite space or duration, for example, may mean that space or time, as known or conceived by us, is without bounds or determinate magnitude. This is perfectly intelligible, and the contradiction of it is conceived as false. But about space and time in themselves, what does infinity, or limitation, or even magnitude, signify? Instead of being, as Hamilton represents them, inconceivable predicates, they are known predicates affirmed of inconceivable subjects. It is not the predicate infinity which it is impossible to conceive, but, according

to Mr. Mill, it is space in itself, since this cannot be made the subject of any judgment.

The extreme inadequacy of our conception of infinite space as a phenomenon is virtually the ground on which Hamilton affirms the inconceivability of infinity as predicated of space in itself, or of any other existence, whether noumenon or phenomenon. This inadequacy amounts to impossibility, according to Hamilton; and he consequently affirms that the conception of infinity is simply the notion of the impossibility of conceiving a magnitude without bounds, — that such a conception is only the negation of conceivability itself as applied to magnitude. But Mr. Mill contends that an infinite magnitude, since it is conceived as one greater than any finite one, implies more than the mere negation of conceivability. It is only partially inconceivable. To say that an infinite magnitude is greater than any other is a positive statement, though we can say or think no more about it. It excludes all we can think definitely and adequately, but it does so in a determinate manner, namely, by affirming that the infinite is greater than the finite. It affirms the direction of the exclusion; and this notion of the infinite is true, as far as it goes, of the space and time known to us. In other words, we know that the space and time of our apprehension exceed any measurable or assignable magnitudes. But how do we know this? Simply because we have found no limits, — not because we cannot conceive of any. The impossibility of conceiving a limit to space is, according to Mr. Mill, a psychological consequence of our experiences of spaces, and proves nothing save by representing these experiences, which are the real sources of all our knowledge of space. The affirmation of infinity is then only a denial of limits to the space of our experience; and it cannot, therefore, be made about what is by hypothesis beyond our capacities of experience, or about space in itself. On the other hand, the denial of infinity is an affirmation of limits; and since this is not given in our experience of space, or in its possibilities as determined by capacities acquired through experience, it is not conceivable at all, either of phenomenal space or space in itself. Space in itself cannot, therefore, be conceived as either limited or unlimited, since the subject is inconceivable. And, on the other hand, space either in itself, or in relation to us and our experience of it, cannot be conceived as limited, since this predication is inconceivable. But if both the propositions are about space in itself, the necessity of admitting one and denying the other, or the impossibility of any third inconceivable supposition, rests on no evidence of experience or acquired limitation of thought, such limitations being already transcended in the subjects of the propositions.

Hamilton holds, of course, that the unconditioned, the subject of his antinomies, is inconceivable, but he denies, in common with nearly all philosophers, that the laws of logic are determined or limited by experience; and with these premises, his main argument is irrefragable. But of these premises the absolutists deny the former, and Mr. Mill the latter. Against these extremes, therefore, his argument is inconclusive, but it follows from the premises of Cousin and many other philosophers. But Mr. Mill not only objects to Hamilton’s application of the ordinary rules of reasoning to propositions about things in themselves, but he joins, as we have seen, with the rest of Hamilton’s critics in opposing his subsidiary arguments, or those for the inconceivability of infinity in general as affirmed of anything. Hamilton attempts, in these arguments, to establish contradiction between inconceivables by an appeal to phenomenal experience itself. He asserts of space, as we know it, that limits and the absence of limits are equally inconceivable, and he therefore attempts a proof of the existence of the unconditioned from the facts and laws of the conditioned itself. The fallacy of this attempt Mr. Mill has sufficiently exposed. Either space, as we know it, has limits or it has no limits. In rejecting, in accordance with experience, the first supposition, we both affirm and conceive the last; but in attempting to realize this fully, we find our faculties inadequate. This inadequacy of conception does not amount, however, to impossibility, unless we attempt to transcend space as we know it, and to conceive of an absolute space, about which nothing whatever is knowable or conceivable. But about this we cannot, then, legitimately appeal to phenomenal experience.

Incidental to his discussion of the law of the Conditioned, the interesting distinction of knowledge and belief, which Mr. Mill does not regard as an important one, is briefly criticised. According to him, knowledge and belief differ only in the degrees of their certainty, or else in the degree of the simplicity and directness of the evidence on which they rest. We fully agree with him in rejecting Hamilton’s doctrine, that belief can rest on any other basis than one of knowledge; but we think it important to scrutinize more closely a distinction which has played so conspicuous a part in religious philosophy. While opinion, belief, and knowledge differ from each other in respect to the degrees of speculative certainty with which anything is held for true, yet these degrees are specifically distinguishable from each other in the philosophical uses of the words. There are, indeed, four distinguishable forms of holding for true, namely, opinion, belief, contingent knowledge, and perfect knowledge; though the limits between the second and third are not precisely fixed by usage. Perfect knowledge cannot be

questioned. It admits of no possible doubt. Contingent knowledge admits of a possible doubt, though not of any actual one. Belief, though not consistently distinguished from the latter, may be limited to what might be questioned on grounds of evidence, though it is practically unquestionable through restraints imposed on our speculative faculties by our moral or practical nature. Such beliefs can be held with an equal degree of certainty with knowledge, though with a certainty of a different kind; being indubitable on account of the limits imposed by the conditions of emotion and the determinations of the will, and not on account of limits from conditions of experience. Such are religious beliefs, which, though inferior to knowledge in speculative certainty, may equal it in practical certainty. And, lastly, opinion is distinguishable from a low degree of simple belief, since it is free from either of these restraints, and admits both of speculative and moral doubts.

The importance of these distinctions comes from the philosophical doctrines they embody; namely, the two orthodox positions, that the difference between science and faith, and the difference between experiential or contingent, and perfect or a priori knowledge, are fundamental ones. Both these positions Mr. Mill rejects, and he departs from orthodox philosophy on the issue, that any beliefs can rightly be held, except on grounds of positive experience, or with a confidence which these do not warrant.

Next in importance and in the order of treatment to the criticisms we have noticed comes Mr. Mill’s examination of Hamilton’s methods and arguments in treating the various topics of phenomenal psychology. The meaning and authority of consciousness, and the rules for its interpretation, are discussed in a manner as much superior to anything which has preceded it on method in psychology, as the philosophy of the modern physical sciences is to the Physics of Aristotle. The fundamental problem of psychology is to determine which of our knowledges are ultimate and which can be supposed to be derivable by intelligible mental processes; and to discriminate these is the object of method in mental science. “The Introspective Method,” by which Mr. Mill designates the method of Hamilton and his school, is a direct appeal to consciousness on this problem, regulated by certain precautions, by the use of which the philosopher is supposed to be superior to the vulgar. By the use of such precautions, Sir William Hamilton proposed to prove, against most philosophers, the vulgar opinion that the external world is an object of immediate perception; and he does this virtually on the ground that the opinion itself seems to a mature consciousness like an axiom, and that the supposition of its truth does not contradict any other fact of consciousness. This is the gist of Hamilton’s

argument. As well might the analogous fundamental question of astronomy, Which moves, the earth or the heavens? be decided, in like manner, by an appeal to the senses.

This comparison suggests a remarkable resemblance between the methods of modern physical science and the “Psychological Method” which Mr. Mill opposes to such an appeal to consciousness. A common characteristic of them is to employ hypotheses, that is, verifiable hypotheses, in order to supplement the facts of observation before deciding upon such questions as the rotation of the earth, or the ultimate simplicity of a fact in consciousness. If the question of psychology had been to determine which of our knowledges are ultimate and which are derived by such mental processes as are cognizable in the present operations of consciousness, the Introspective Method would have been complete. But then a further question would require answer. Are there not present states of consciousness apparently simple, but really the results of past and long-forgotten mental processes? Have not, for example, our present ideas of externality and extension such an origin? Introspection of present consciousness cannot decide this; but this is the real question between Sir William Hamilton and the idealists as represented by Mr. Mill. Just as the analogous question of astronomy was decided against the vulgar in the Copernican system, so a really scientific application of the ‘‘Psychological Method” decides against the vulgar on this question; and as the dynamical laws of matter placed the Copernican system on a firm, irrefragable basis, so the mental laws of association are made the foundation of idealistic psychology. For if the ideas of externality and extension can be shown to be derivable, though not by present or remembered processes, yet by intelligible ones, they cannot be regarded as simple merely on the authority of present consciousness. The only limit to the application of the law of inseparable association as an hypothesis to explain the origin of ideas from simple feelings, must be in its inability to make this genesis distinctly intelligible; and here is the weak point of associational psychology, and one in which, with its present attainments, it fails to resemble the science of astronomy with which we have compared it. But Mr. Mill and Mr. Bain (whom he quotes on several points of interest) have done much to show how this failure may in future be remedied, when psychology shall have come out completely from that region of dogmatic metaphysics in which Sir William Hamilton leaves it, to become one in the sisterhood of the modern sciences.

Mr. Mill’s criticisms of Hamilton’s logical doctrines are not less fundamental than those on his metaphysics and psychology. Very few indeed of the opinions which are original or essential to Sir William Hamilton

find acceptance with his critic. But this is not surprising, when we see how fundamentally their philosophies differ. What will surprise the reader most are the numerous contradictions and inconsistencies in Hamilton’s writings which his critic has pointed out. The principal of these we have tried to explain as arising from misinterpretations of his doctrines. There are enough remaining, however, to greatly impair his reputation, before unchallenged, for profundity and accuracy, and even for scholarship.