In philosophy, a noumenon (, ; from ; : noumena) is knowledge posited as an object that exists independently of human sense. The term noumenon is generally used in contrast with, or in relation to, the term phenomenon, which refers to any object of the senses. Immanuel Kant first developed the notion of the noumenon as part of his transcendental idealism, suggesting that while we know the noumenal world to exist because human sensibility is merely receptive, it is not itself sensible and must therefore remain otherwise unknowable to us. In Kantian philosophy, the noumenon is often associated with the unknowable "thing-in-itself" (). However, the nature of the relationship between the two is not made explicit in Kant's work, and remains a subject of debate among Kant scholars as a result.
Etymology The Greek word (plural ) is the neuter middle-passive present participle of , which in turn originates from the word , an Attic contracted form of ., , . A rough equivalent in English would be "that which is thought", or "the object of an act of thought".
Historical predecessors The Indian Vedānta philosophy (specifically Advaita), the roots of which go back to the Vedic period, talks of the ātman (self) in similar terms as the noumenon.
Regarding the equivalent concepts in Plato, Ted Honderich writes: "Platonic Ideas and Forms are noumena, and phenomena are things displaying themselves to the senses... This dichotomy is the most characteristic feature of Plato's dualism; that noumena and the noumenal world are objects of the highest knowledge, truths, and values is Plato's principal legacy to philosophy."
Kantian noumena
Overview As expressed in Kant's Critique of Pure Reason, human understanding is structured by "concepts of the understanding" or pure categories of understanding, found prior to experience in the mind and which make outer experiences possible as counterpart to the rational faculties of the mind.Hanna, Robert (2009). Completing the Picture of Kant's Metaphysics of Judgment. Stanford Encyclopedia of Philosophy.Stanford Encyclopedia of Philosophy on Kant's metaphysics.
By Kant's account, when one employs a concept to describe or categorize noumena (the objects of inquiry, investigation, or analysis of the workings of the world), one is also employing a way of describing or categorizing phenomena (the observable manifestations of those objects of inquiry, investigation or analysis). Kant posited methods by which human understanding makes sense of and thus intuits phenomena that appear to the mind: the concepts of the transcendental aesthetic, as well as that of the transcendental analytic, transcendental logic and transcendental deduction.The Encyclopedia of Philosophy (Macmillan, 1967, 1996) Volume 4, "Kant, Immanuel", section on "Critique of Pure Reason: Theme and Preliminaries", p. 308 ff.The Encyclopedia of Philosophy (Macmillan, 1967, 1996) Volume 4, "Kant, Immanuel", section on "Transcendental Aesthetic", p. 310 ff.The Encyclopedia of Philosophy (Macmillan, 1967, 1996) Volume 4, "Kant, Immanuel", section on "Pure Concepts of the Understanding", p. 311 ff. Taken together, Kant's "categories of understanding" are the principles of the human mind which necessarily are brought to bear in attempting to understand the world in which we exist (that is, to understand, or attempt to understand, "things in themselves"). In each instance the word "transcendental" refers to the process that the human mind must exercise to understand or grasp the form of, and order among, phenomena. Kant asserts that to "transcend" a direct observation or experience is to use reason and classifications to strive to correlate with the phenomena that are observed. Humans can make sense out of phenomena in these various ways, but in doing so can never know the "things-in-themselves", the actual objects and dynamics of the natural world in their noumenal dimension - this being the negative, correlate to phenomena and that which escapes the limits of human understanding. By Kant's Critique, our minds may attempt to correlate in useful ways, perhaps even closely accurate ways, with the structure and order of the various aspects of the universe, but cannot know these "things-in-themselves" (noumena) directly. Rather, we must infer the extent to which the human rational faculties can reach the object of "things-in-themselves" by our observations of the manifestations of those things that can be perceived via the physical senses, that is, of phenomena, and by ordering these perceptions in the mind help infer the validity of our perceptions to the rational categories used to understand them in a rational system. This rational system (transcendental analytic), being the categories of the understanding as free from empirical contingency.See, e.g., The Encyclopedia of Philosophy (Macmillan, 1967, 1996) Volume 4, "Kant, Immanuel", section on "Critique of Pure Reason: Theme and Preliminaries", p. 308 ff.See also, e.g., The Encyclopedia of Philosophy (Macmillan, 1967, 1996) Volume 4, "Kant, Immanuel", section on "Pure Concepts of the Understanding", p. 311 ff.
According to Kant, objects of which we are cognizant via the physical senses are merely representations of unknown somethings—what Kant refers to as the transcendental object—as interpreted through the a priori or categories of the understanding. These unknown somethings are manifested within the noumenon—although we can never know how or why as our perceptions of these unknown somethings via our physical senses are bound by the limitations of the categories of the understanding and we are therefore never able to fully know the "thing-in-itself".
Noumenon and the thing-in-itself Many accounts of Kant's philosophy treat "noumenon" and "thing-in-itself" as synonymous, and there is textual evidence for this relationship.Immanuel Kant (1781) Critique of Pure Reason, for example in A254/B310, p. 362 (Guyer and Wood), "The concept of a noumenon, i.e., of a thing that is not to be thought of as an object of the senses but rather as a thing-in-itself [...]"; But note that the terms are not used interchangeably throughout. The first reference to thing-in-itself comes many pages (A30) before the first reference to noumenon (A250). For a secondary or tertiary source, see: "Noumenon" in the Encyclopædia Britannica But Stephen Palmquist holds that "noumenon" and "thing-in-itself" are only loosely synonymous, inasmuch as they represent the same concept viewed from two different perspectives,"Noumenon: the name given to a thing when it is viewed as a transcendent object. The term 'negative noumenon' refers only to the recognition of something which is not an object of sensible intuition, while 'positive noumenon' refers to the (quite mistaken) attempt to know such a thing as an empirical object. These two terms are sometimes used loosely as synonyms for 'transcendental object' and 'thing-in-itself', respectively. (Cf. phenomenon.)" – Glossary of Kant's Technical TermsThing-in-itself: an object considered transcendentally apart from all the conditions under which a subject can gain knowledge of it via the physical senses. Hence the thing-in-itself is, by definition, unknowable via the physical senses. Sometimes used loosely as a synonym of noumenon. (Cf. appearance.)" – Glossary of Kant's Technical Terms. Palmquist defends his definitions of these terms in his article, "Six Perspectives on the Object in Kant's Theory of Knowledge", Dialectica 40:2 (1986), pp.121–151; revised and reprinted as Chapter VI in Palmquist's book, Kant's System of Perspectives (Lanham: University Press of America, 1993). and other scholars also argue that they are not identical.Oizerman, T. I., "Kant's Doctrine of the "Things in Themselves" and Noumena", Philosophy and Phenomenological Research, Vol. 41, No. 3, Mar., 1981, 333–350; Karin de Boer, "Kant's Multi-Layered Conception of Things in Themselves, Transcendental Objects, and Monads", Kant-Studien 105/2, 2014, 221-260. Schopenhauer criticised Kant for changing the meaning of "noumenon". But this opinion is far from unanimous."Other interpreters have introduced an almost unending stream of varying suggestions as to how these terms ought to be used. A handful of examples will be sufficient to make this point clear, without any claim to represent an exhaustive overview. Perhaps the most commonly accepted view is expressed by Paulsen, who equates 'thing-in-itself' and 'noumenon', equates 'appearance' and 'phenomenon', distinguishes 'positive noumenon' and 'negative noumenon', and treats 'negative noumenon' as equivalent to 'transcendental object' [pp. 4:148-50, 154-5, 192]. Al-Azm and Wolff also seem satisfied to equate 'phenomenon' and 'appearance', though they both carefully distinguish 'thing-in-itself' from 'negative noumenon' and 'positive noumenon' [A4:520; W21:165, 313–5; s.a. W9:162]. Gotterbarn similarly equates the former pair, as well as 'thing-in-itself' and 'positive noumenon', but distinguishes between 'transcendental object', 'negative noumenon' and 'thing-in-itself' [G11: 201]. By contrast, Bird and George both distinguish between 'appearance' and 'phenomenon', but not between 'thing-in-itself' and 'noumenon' [B20:18,19, 53–7; G7:513-4n]; and Bird sometimes blurs the distinction between 'thing-in-itself' and 'transcendental object' as well. Gram equates 'thing-in-itself' not with 'noumenon', but with 'phenomenon' [G13:1,5-6]! Allison cites different official meanings for each term, yet he tends to equate 'thing-in-itself' at times with 'negative noumenon' and at times with 'transcendental-object', usually ignoring the role of the 'positive noumenon' [A7:94; A10:58,69]. And Buchdahl responds to the fact that the thing-in-itself seems to be connected with each of the other object-terms by regarding it as 'Kant's umbrella term'." Stephen Palmquist on Kant's object terms Kant's writings show points of difference between noumena and things-in-themselves. For instance, he regards things-in-themselves as existing:
though we cannot know these objects as things in themselves, we must yet be in a position at least to think them as things in themselves; otherwise we should be landed in the absurd conclusion that there can be appearance without anything that appears.
He is much more doubtful about noumena: But in that case a noumenon is not for our understanding a special [kind of] object, namely, an intelligible object; the [sort of] understanding to which it might belong is itself a problem. For we cannot in the least represent to ourselves the possibility of an understanding which should know its object, not discursively through categories, but intuitively in a non-sensible intuition.
A crucial difference between the noumenon and the thing-in-itself is that to call something a noumenon is to claim a kind of knowledge, whereas Kant insisted that the thing-in-itself is unknowable. Interpreters have debated whether the latter claim makes sense: it seems to imply that we know at least one thing about the thing-in-itself (i.e., that it is unknowable). But Palmquist argues that this is part of Kant's definition of the term, to the extent that anyone who claims to have found a way of making the thing-in-itself knowable must be adopting a non-Kantian position."The Radical Unknowability of Kant's 'Thing in Itself'", Cogito 3:2 (March 1985), pp.101–115; revised and reprinted as Appendix V in Stephen Palmquist, Kant's System of Perspectives (Lanham: University Press of America, 1993).
Positive and negative noumena Kant also distinguishes between positive and negative noumena:Mattey, G. J.Lecture notes by G. J. Mattey If by 'noumenon' we mean a thing so far as it is not an object of our sensible intuition, and so abstract from our mode of intuiting it, this is a noumenon in the negative sense of the term.