Hamilton, William (1788–1856)

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William Hamilton, the Scottish philosopher and logician, was born in Glasgow and was educated at Glasgow, at Edinburgh, and at Balliol College, Oxford, where he took his B.A. in 1811. After leaving Oxford he studied law and in 1813 was admitted to the Scottish bar. He was appointed professor of civil history at the University of Edinburgh in 1821 and was elected to the chair of logic and metaphysics in 1836. Hamilton, a man of stupendous erudition, was strongly influenced by Thomas Reid and Immanuel Kant.


Hamilton divided "mental modifications, or phenomena" into three classesthe phenomena of knowledge or cognition; the phenomena of feeling, of pleasure and pain; and the phenomena of will or desire, the exertive or connative powers. Knowledge, feeling, and will or desire cannot exist independently of one another. Every state of mind is a combination of all three, although proportions may vary. We can conceive of a being who knows one thing or another but is totally devoid of feeling, desire, and volition; or of a being capable of knowledge and feeling only; but not of a being having the capacity for pleasure and pain and the capacity to will, but lacking the faculty of knowledge.

Mental phenomena are included under the phenomenon of consciousness. When one knows, he knows or is conscious that he knows; when one feels, he knows or is conscious that he feels; and when one desires, he knows or is conscious that he desires. Consciousness is not something in addition to knowledge, feeling, and desire, but the general condition of their existence. It is a relation between a knowing (or conscious, or intelligent) subject and an object of knowledge, in this case a modification of the mind. Although Hamilton sometimes denied the possibility of unconscious mental states, at other times he argued that "the mind exerts energies, and is the subject of modifications, of neither of which it is conscious" (Lectures on Metaphysics, Lecture 18).


In perception, according to Hamilton, we have an immediate or presentative rather than a mediate or representative knowledge of the object. In presentative cognition a thing is known in itself rather than via something other than itself. When I see a cat I come to know the animal in itself as contrasted with, for example, my knowledge of a past event, which is acquired through testimonials and other means distinct from the event thus cognized. I may have representative knowledge of the past, the future, and the merely possible, as in imagination. Immediate presentative knowledge is of that which exists here and now. Perception is the faculty presentative of the phenomena of the nonego (matter), and self-consciousness is the faculty presentative of the phenomena of the ego (mind). A thing is known in itself only if it be known as actually existing in its when (now) and its where (here). Perception has for its objects the primary qualities of bodies. Knowledge of secondary qualities is never immediate, in that all we can know of them is that some unknown external cause is responsible for the "present affections of the conscious subject." Thus Hamilton agreed with Thomas Reid that we have a "direct notion" of primary qualities but only relative notions of the secondary qualities of things.

In perception we are intuitively aware of the duality of ego and nonego. This is an immediate, primitive datum of consciousness, to whose existence the natural realist (or natural dualistboth terms were used by Hamilton to designate holders of views like his own) is implicitly committed. Perception is not inference. We do not first become aware of some mode of consciousness and then infer from this awareness the present existence of a physical object as cause of that modification. Nor are we aware of an inner representation or referent from which we conclude the existence of an object referred to or represented. Representative theories of perception presuppose what on their own terms could not be the case. In order to know that A refers to or represents or is a sign of B, it must be possible to gain knowledge of the existence and nature of B independently of our knowledge of the existence and nature of A.

Relativity of Knowledge

Granting that our senses inform us of the existence and the nature of physical objects, just what information do they provide us with? Hamilton held that our knowledge of mind and of matter is relative and conditioned and that "of existence absolutely and in itself, we know nothing" (Lectures on Metaphysics, Lecture 8). Our knowledge of the ego as well as of the nonego is purely phenomenal. The self is known to us only via the phenomena of the immediate introspective awareness of the flow of experience. In external perception we come to know about physical objects only as they appear to us through the senses. A physical object as known is that which appears to us as extended, solid, divisible, figured, colored, hot or cold. Thus, "matter" or "body" is a name for a certain set of appearances or phenomena, but these must be regarded as appearances of something. This something, however, is inconceivable apart from its phenomena, absolutely and in itself, out of relation to a knower. By virtue of a "law of thought" we are compelled to think of something absolute, unknown, and unknowable as the subject, substance, or substratum of the relative, the phenomenal, the known. The same reasoning applies to mind.

That a thing or a quality of a thing is known in itself does not mean that it is known in its "absolute existence" out of relation to the knower, for this is impossible. Hamilton meant, presumably, only that it is not known through a process of inference from signs or representations. All knowledge is relative in that in order to be known a thing must be related to the knower, the relation being precisely that of the knower to the known. But this is trivial. Hamilton pointed out that the way a thing appears to us in perception is relative in another senseit is a function not only of the objective qualities of the thing, but of the medium and the sense organs as well. When I perceive a book, the phenomena or appearances of the external object are a resultant of the contributions of the book, of the intervening medium, and of the sense organs. Consequently my knowledge of the book is modified through certain intermediate agencies and must be relative. But, as J. S. Mill pointed out in An Examination, this conclusion does not follow; rather than entailing the relativity of all knowledge of physical objects, the considerations adduced show at most that that part of the knowledge that is not contributed by the book itself is relative.

Philosophy of the Conditioned

To think of a thing is necessarily to think of it as a thing of a certain sort, to classify it, to subsume it under a concept. Thought imposes conditions on its object. Therefore the conditioned is the only possible object of knowledge. The absolute, the nonrelative, the unconditioned is inconceivable; all we can know is that it is, not what it is. Although many things are inconceivable to us, nonetheless we know that some of them must be true. Hamilton claimed that, given the principles of contradiction and excluded middle, all actual thought lies between two extremes, each of which is inconceivable. The extremes represent that which is absolute or unconditioned. One of these absolutes we know must be true because they are mutually contradictory; but since both are inconceivable we cannot know which is true. "The Conditioned is the mean between two extremestwo unconditionates, exclusive of each other neither of which can be conceived as possible, but of which one must be admitted as necessary" (Discussions, p. 22). The weakness of the human mind thus restricts its objects of positive thought to the mean. As illustration Hamilton argued that space must either be bounded or unbounded. One alternative must be true, but both cannot be, even though we cannot positively conceive of either one. Similarly we cannot conceive of an absolute beginning of time or of an infinite regress. We cannot conceive of an absolute end of time or of an infinite prolongation, although one or the other must be admitted to be true.


Hamilton regarded his doctrine of the quantification of the predicate as his most important contribution to logic. The doctrine is based on the self-evident truth that we can operate rationally only with what we already understand. This in turn leads to the postulate that we ought to be able to state explicitly what is thought implicitly. When we make a judgment we always implicitly understand the quantity of the predicate as well as the quantity of the subject. Since the predicate is always quantified in thought, and since every quantity is either all or some or none, we always regard the predicate of a judgment as denoting all, some, or none of the objects in its extension. The proposition "All men are animals" must mean either that all men are all animals (all men and only men are animals), or that all men are some animals (all men, but not men only, are animals) "Some animals are carnivorous" becomes "Some animals are some carnivorous," which is to be understood as some and some only, that is, some animals are carnivorous and some are not. Among the advantages of this innovation, according to Hamilton, are the reduction of propositions to equations, the simplification of the doctrine of conversion, the abolition of the figured syllogism and the consequent manifestation of the absurdity of reducing syllogisms of other figures to the first.

Since in Hamilton's view logic is the science of the laws that of necessity govern all valid thought, criticisms of him drawn from psychological considerations are relevant. It comes as something of a surprise to the beginner in logic that conversion of the universal affirmative "All S is P " is only by limitation to "Some P is S." But in Hamilton's view this should be obvious to all and should not represent a new idea as in fact it does.

See also Kant, Immanuel; Logic, History of; Perception; Phenomenology; Psychology; Reid, Thomas.


works by hamilton

Original Philosophy

"On the Philosophy of the Unconditioned." Edinburgh Review 1 (1829): 194221.

Discussions on Philosophy and Literature, Education and University Reform. London: Longman, Brown, Green and Longmans, 1852.

Lectures on Metaphysics and Logic. Edited by H. L. Mansel and John Veitch, 4 vols. Edinburgh and Boston: Blackwood, 18591860.

Editing and Commentary

The Works of Thomas Reid. 2 vols. Edinburgh, 1846. Hamilton edited this work and added important commentaries.

The Works of Dugald Stewart. 11 vols. Edinburgh, 18541856. Hamilton edited this work.

works on hamilton

Grave, S. A. The Scottish Philosophy of Common Sense. Oxford: Clarendon Press, 1960.

Mill, John Stuart. An Examination of Sir William Hamilton's Philosophy. 2 vols. London: Longman, Green, Longman, Roberts and Green, 1865.

Rasmussen, S. V. The Philosophy of Sir William Hamilton. Copenhagen, 1925.

Stirling, J. H. Sir William Hamilton. London: Longmans, Green, 1865.

Veitch, John. Hamilton. Edinburgh: Blackwood, 1882.

Wight, O. W. Philosophy of Sir William Hamilton. New York: Appleton, 1853.

Timothy J. Duggan (1967)

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Hamilton, William (1788–1856)

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