Editing Theory of categories

{{Short description|In ontology, the highest kinds or genera of entities}}
{{Distinguish|Category theory}}

In [[ontology]], the '''theory of categories''' concerns itself with the ''categories of being'': the highest ''genera'' or ''kinds of entities''.<ref name="Thomasson2">{{cite web |last1=Thomasson |first1=Amie |title=Categories |url=https://plato.stanford.edu/entries/categories/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=4 January 2021 |date=2019}}</ref> To investigate the categories of being, or simply '''categories''', is to determine the most fundamental and the broadest [[class (philosophy)|class]]es of entities.<ref>{{cite journal |last1=Mcdaniel |first1=Kris |title=A Return to the Analogy of Being |journal=Philosophy and Phenomenological Research |date=2010 |volume=81 |issue=3 |pages=688–717 |doi=10.1111/j.1933-1592.2010.00378.x |url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1933-1592.2010.00378.x |language=en |issn=1933-1592}}</ref> A distinction between such categories, in making the categories or applying them, is called an '''ontological distinction'''. Various systems of categories have been proposed, they often include categories for [[Substance (philosophy)|substances]], [[Property (philosophy)|properties]], [[Relations (philosophy)|relations]], [[states of affairs]] or [[Event (philosophy)|events]].<ref name="Sandkühler2">{{cite book |last1=Sandkühler |first1=Hans Jörg |title=Enzyklopädie Philosophie |date=2010 |publisher=Meiner |url=https://meiner.de/enzyklopadie-philosophie.html |chapter=Ontologie: 4 Aktuelle Debatten und Gesamtentwürfe |access-date=2021-01-14 |archive-date=2021-03-11 |archive-url=https://web.archive.org/web/20210311040207/https://meiner.de/enzyklopadie-philosophie.html |url-status=dead }}</ref><ref name="Borchert2">{{cite book |last1=Borchert  |first1=Donald |title=Macmillan Encyclopedia of Philosophy, 2nd Edition |date=2006 |publisher=Macmillan |url=https://philpapers.org/rec/MONMEO-3 |chapter=Ontology}}</ref> A representative question within the theory of categories might articulate itself, for example, in a query like, "[[Problem of universals|Are universals prior to particulars?]]"

==Early development==
The process of abstraction required to discover the number and names of the categories of being has been undertaken by many philosophers since [[Aristotle]] and involves the careful inspection of each concept to ensure that there is no higher category or categories under which that concept could be subsumed.<ref>{{Cite web |title=The Internet Classics Archive {{!}} Categories by Aristotle |url=http://classics.mit.edu/Aristotle/categories.1.1.html |access-date=2022-07-15 |website=classics.mit.edu}}</ref> The [[Scholasticism|scholars]] of the twelfth and thirteenth centuries developed Aristotle's ideas.<ref>{{Citation |last1=Gracia |first1=Jorge |title=Medieval Theories of the Categories |date=2016 |url=https://plato.stanford.edu/archives/win2016/entries/medieval-categories/ |encyclopedia=The Stanford Encyclopedia of Philosophy |editor-last=Zalta |editor-first=Edward N. |edition=Winter 2016 |publisher=Metaphysics Research Lab, Stanford University |access-date=2022-07-15 |last2=Newton |first2=Lloyd}}</ref> For example, [[Gilbert de la Porrée|Gilbert of Poitiers]] divides Aristotle's ten categories into two sets, primary and secondary, according to whether they inhere in the subject or not:
*Primary categories: Substance, Relation, Quantity and Quality
*Secondary categories: Place, Time, Situation, Condition, Action, Passion<ref>Reese W.L. ''Dictionary of Philosophy and Religion'' (Harvester Press, 1980)</ref>
Furthermore, following [[Porphyry (philosopher)|Porphyry]]’s likening of the classificatory hierarchy to a [[Porphyrian tree|tree]], they concluded that the major classes could be subdivided to form subclasses, for example, [[Substance theory|Substance]] could be divided into [[Genus]] and Species, and [[Quality (philosophy)|Quality]] could be subdivided into [[Property (philosophy)|Property]] and Accident, depending on whether the property was necessary or contingent.<ref>''Ibid''. cf Evangelou C. ''Aristotle's Categories and Porphyry'' (E.J. Brill, Leiden, 1988)</ref> An alternative line of development was taken by [[Plotinus]] in the second century who by a process of abstraction reduced Aristotle's list of ten categories to five: Substance, Relation, Quantity, Motion and Quality.<ref>Plotinus ''Enneads'' (tr. Mackenna S. & Page B.S., The Medici Society, London, 1930) VI.3.3</ref> Plotinus further suggested that the latter three categories of his list, namely Quantity, Motion and Quality correspond to three different kinds of relation and that these three categories could therefore be subsumed under the category of Relation.<ref>''Ibid''. VI.3.21</ref> This was to lead to the supposition that there were only two categories at the top of the hierarchical tree, namely Substance and Relation. Many supposed that relations only exist in the mind. Substance and Relation, then, are closely commutative with Matter and Mind--this is expressed most clearly in the dualism of [[René Descartes]].<ref>Descartes R. ''The Philosophical Works of Descartes'' (tr. Haldane E. & Ross G., Dover, New York, 1911) Vol.1</ref>

===Vaisheshika===
{{excerpt|Padārtha|only=paragraphs}}

===Stoic===
{{excerpt|Stoicism|Categories}}

===Aristotle===
{{Main|Categories (Aristotle)}}

One of [[Aristotle]]’s early interests lay in the classification of the natural world, how for example the genus "animal" could be first divided into "two-footed animal" and then into "wingless, two-footed animal".<ref>Aristotle ''Metaphysics'' 1075a</ref> He realised that the distinctions were being made according to the qualities the animal possesses, the quantity of its parts and the kind of motion that it exhibits. To fully complete the proposition "this animal is&nbsp;..." Aristotle stated in his work on the [[Categories (Aristotle)|Categories]] that there were ten kinds of predicate where&nbsp;...

"...&nbsp;each signifies either substance or quantity or quality or relation or where or when or being-in-a-position or having or acting or being acted upon".<ref>''Op.cit.2''</ref>

He realised that predicates could be simple or complex. The simple kinds consist of a subject and a predicate linked together by the "categorical" or inherent type of relation. For Aristotle the more complex kinds were limited to propositions where the predicate is compounded of two of the above categories for example "this is a horse running". More complex kinds of proposition were only discovered after Aristotle by the Stoic, [[Chrysippus]],<ref>Long A. & Sedley D. ''The Hellenistic Philosophers'' (Cambridge University Press, 1987) p.206</ref> who developed the "hypothetical" and "disjunctive" types of [[syllogism]] and these were terms which were to be developed through the [[Scholasticism|Middle Ages]]<ref>Peter of Spain (''alias'' John XXI) ''Summulae Logicales''</ref> and were to reappear in [[Category (Kant)|Kant's system of categories]].

''Category'' came into use with [[Aristotle]]'s essay ''[[Categories (Aristotle)|Categories]]'', in which he discussed univocal and [[Equivocation|equivocal]] terms, predication, and ten categories:<ref>''[http://www.gutenberg.org/files/2412/2412-h/2412-h.htm Categories]'', translated by [[Ella Mary Edghill|E. M. Edghill]]. For the Greek terms, see ''[http://meta.montclair.edu/ancient/greek/aristotle_greek/ The Complete Works of Aristotle in Greek] {{Webarchive|url=https://web.archive.org/web/20100401112540/http://meta.montclair.edu/ancient/greek/aristotle_greek/ |date=2010-04-01 }}'' (requires DjVu), Book 1 (''Organon''), ''Categories'' Section 4 (DjVu file's page 6).{{cite web |url=http://www.gutenberg.org/files/2412/2412-h/2412-h.htm |title=The Project Gutenberg E-text of the Categories, by Aristotle |access-date=2010-02-21 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20131102084057/http://www.gutenberg.org/files/2412/2412-h/2412-h.htm |archive-date=2013-11-02 }}</ref>
*'''[[Substance theory|Substance]]''', essence (''[[ousia]]'') – examples of primary substance: this man, this horse; secondary substance (species, genera): man, horse
*'''[[Quantity]]''' (''poson'', how much), discrete or continuous – examples: two cubits long, number, space, (length of) time.
*'''[[Quality (philosophy)|Quality]]''' (''poion'', of what kind or description) – examples: white, black, grammatical, hot, sweet, curved, straight.
*'''[[Property (philosophy)|Relation]]''' (''pros ti'', toward something) – examples: double, half, large, master, knowledge.
*'''[[Space|Place]]''' (''pou'', where) – examples: in a marketplace, in the Lyceum
*'''[[Time]]''' (''pote'', when) – examples: yesterday, last year
*'''[[Human position|Position]]''', posture, attitude (''keisthai'', to lie) – examples: sitting, lying, standing
*'''State''', [[Condition (philosophy)|condition]] (''echein'', to have or be) – examples: shod, armed
*'''[[Action (philosophy)|Action]]''' (''poiein'', to make or do) – examples: to lance, to heat, to cool (something)
*'''[[Affection (philosophy)|Affection]]''', passion (''paschein'', to suffer or undergo) – examples: to be lanced, to be heated, to be cooled

===Plotinus===
[[Plotinus]] in writing his ''[[Enneads]]'' around AD 250 recorded that "Philosophy at a very early age investigated the number and character of the existents&nbsp;... some found ten, others less&nbsp;... to some the genera were the first principles, to others only a generic classification of existents."<ref>''Op.cit.9'' VI.1.1</ref> He realised that some categories were reducible to others saying "Why are not Beauty, Goodness and the virtues, Knowledge and Intelligence included among the primary genera?"<ref>''Ibid.'' VI.2.17</ref> He concluded that such [[Transcendentals|transcendental categories]] and even the [[Categories (Aristotle)|categories of Aristotle]] were in some way posterior to the three [[Eleatics|Eleatic]] categories first recorded in Plato's dialogue ''[[Parmenides (dialogue)|Parmenides]]'' and which comprised the following three coupled terms: 
*Unity/Plurality
*Motion/Stability
*Identity/Difference<ref>Plato ''Parmenides'' (tr. Jowett B., ''The Dialogues of Plato'', Clarendon Press, Oxford, 1875) p.162</ref>

[[Plotinus]] called these "the hearth of reality"<ref>''Op.cit.9'' Op.cit.1.4</ref> deriving from them not only the three categories of Quantity, Motion and Quality but also what came to be known as "the three moments of the [[Neoplatonism|Neoplatonic world process]]":
*First, there existed the "One", and his view that "the origin of things is a contemplation"
*The Second "is certainly an activity&nbsp;... a secondary phase&nbsp;... life streaming from life&nbsp;... energy running through the universe"
*The Third is some kind of Intelligence concerning which he wrote "Activity is prior to Intellection&nbsp;... and self knowledge"<ref>''Ibid.'' III.8.5</ref>

Plotinus likened the three to the centre, the radii and the circumference of a circle, and clearly thought that the principles underlying the categories were the first principles of creation. "From a single root all being multiplies." Similar ideas were to be introduced into Early Christian thought by, for example, [[Gregory of Nazianzus]] who summed it up saying "Therefore, Unity, having from all eternity arrived by motion at duality, came to rest in [[Trinity]]."<ref>Rawlinson A.E. (ed.) ''Essays on the Trinity and the Incarnation'' (Longmans, London, 1928) pp.241-244</ref>

==Modern development==
Kant and Hegel accused the Aristotelian table of categories of being '[[Wiktionary:rhapsodic|rhapsodic]]', derived arbitrarily and in bulk from experience, without any systematic [[necessity (logic)|necessity]].<ref>{{cite journal|author=[[Enrico Berti]]|url=https://journals-openedition-org.translate.goog/estetica/2024?_x_tr_sl=it&_x_tr_tl=en&_x_tr_hl=it&_x_tr_pto=wapp|title=Sono ancora utili oggi le categorie di Aristotele?|journal=Nuove Ontologie|number=39|year=2008|doi=10.4000/estetica.2024|pages=57–72|language=it|doi-access=free}}</ref>

The early modern dualism, which has been described above, of Mind and Matter or Subject and Relation, as reflected in the writings of Descartes underwent a substantial revision in the late 18th century. The first objections to this stance were formulated in the eighteenth century by [[Immanuel Kant]] who realised that we can say nothing about [[Substance theory|Substance]] except through the relation of the subject to other things.<ref>''Op.cit.3'' p.87</ref> 

For example: In the sentence "This is a house" the substantive subject "house" only gains meaning in relation to human use patterns or to other similar houses. The category of Substance disappears from [[Category (Kant)|Kant's tables]], and under the heading of Relation, Kant lists ''inter alia'' the three relationship types of Disjunction, Causality and Inherence.<ref>''Ibid.'' pp.107,113</ref> The three older concepts of Quantity, Motion and Quality, as [[Charles Sanders Peirce|Peirce]] discovered, could be subsumed under these three broader headings in that [[Quantity]] relates to the subject through the relation of [[Logical disjunction|Disjunction]]; Motion relates to the subject through the relation of [[Causality]]; and [[Quality (philosophy)|Quality]] relates to the subject through the relation of [[Inherence]].<ref>''Op.cit.5'' pp.148-179</ref> Sets of three continued to play an important part in the nineteenth century development of the categories, most notably in [[Georg Wilhelm Friedrich Hegel|G.W.F. Hegel's]] extensive tabulation of categories,<ref>Stace W.T. ''The Philosophy of Hegel'' (Macmillan & Co, London, 1924)</ref> and in [[Categories (Peirce)|C.S. Peirce's categories]] set out in his work on the logic of relations. One of Peirce's contributions was to call the three primary categories Firstness, Secondness and Thirdness<ref>''Op.cit.5'' pp.148-179</ref> which both emphasises their general nature, and avoids the confusion of having the same name for both the category itself and for a concept within that category.

In a separate development, and building on the notion of primary and secondary categories introduced by the Scholastics, [[Immanuel Kant|Kant]] introduced the idea that secondary or "derivative" categories could be derived from the primary categories through the combination of one primary category with another.<ref>''Op.cit.3'' p.116</ref> This would result in the formation of three secondary categories: the first, "Community" was an example that Kant gave of such a derivative category; the second, "[[Linguistic modality|Modality]]", introduced by Kant, was a term which Hegel, in developing Kant's dialectical method, showed could also be seen as a derivative category;<ref>Hegel G.W.F. ''Logic'' (tr. Wallace W., Clarendon Press, Oxford, 1975) pp.124ff</ref> and the third, "Spirit" or "Will" were terms that [[Georg Wilhelm Friedrich Hegel|Hegel]]<ref>''Op.cit.15''</ref> and [[Arthur Schopenhauer|Schopenhauer]]<ref>Schopenhauer A. ''On the Four-Fold Root of the Principle of Sufficient Reason''  1813 (tr. Payne E., La Salle, Illinois, 1974)</ref> were developing separately for use in their own systems. [[Karl Jaspers]] in the twentieth century, in his development of existential categories, brought the three together, allowing for differences in terminology, as Substantiality, Communication and Will.<ref>Jaspers K. ''Philosophy'' 1932 (tr. Ashton E.B., University of Chicago Press, 1970) pp.117ff</ref> This pattern of three primary and three secondary categories was used most notably in the nineteenth century by [[Peter Mark Roget]] to form the six headings of his [[Roget's Thesaurus|Thesaurus]] of English Words and Phrases. The headings used were the three objective categories of Abstract Relation, Space (including Motion) and Matter and the three subjective categories of Intellect, Feeling and Volition, and he found that under these six headings all the words of the English language, and hence any possible predicate, could be assembled.<ref>Roget P.M. ''Roget's Thesaurus: The Everyman Edition'' 1952 (Pan Books, London, 1972)</ref>

===Kant===
{{main|Category (Kant)}}

In the ''[[Critique of Pure Reason]]'' (1781), [[Immanuel Kant]] argued that the [[Category (Kant)|categories]] are part of our own mental structure and consist of a set of ''a priori'' concepts through which we interpret the world around us.<ref>	''Op.cit.3'' p.87</ref> These concepts correspond to twelve logical functions of the understanding which we use to make judgements and there are therefore two tables given in the ''Critique'', one of the Judgements and a corresponding one for the [[Category (Kant)|Categories]].<ref>''Ibid.'' pp.107,113</ref> To give an example, the logical function behind our reasoning from ground to consequence (based on the [[Hypothetical syllogism|Hypothetical relation]]) underlies our understanding of the world in terms of cause and effect (the [[Causality|Causal relation]]). In each table the number twelve arises from, firstly, an initial division into two: the Mathematical and the Dynamical; a second division of each of these headings into a further two: Quantity and Quality, and Relation and Modality respectively; and, thirdly, each of these then divides into a further three subheadings as follows.

{{col-begin}}
{{col-break}}
Table of Judgements

Mathematical
*Quantity
**Universal
**Particular
**Singular
*Quality
**Affirmative
**Negative
**Infinite
Dynamical
*Relation
**Categorical
**Hypothetical
**Disjunctive
*Modality
**Problematic
**Assertoric
**Apodictic
{{col-break}}
Table of Categories

Mathematical
*[[Quantity]]
**Unity
**Plurality
**[[Absolute (philosophy)|Totality]]
*[[Quality (philosophy)|Quality]]
**[[Reality]]
**[[Negation]]
**Limitation
Dynamical
*[[Relation of Ideas|Relation]]
**[[Inherence]] and [[Subsistence economy|Subsistence]] ([[Substance theory|substance]] and [[accident]])
**[[Causality]] and Dependence ([[cause]] and [[Result|effect]])
**Community (reciprocity)
*[[Modal logic|Modality]]
**[[Logical possibility|Possibility]]
**[[Existence]]
**[[Need|Necessity]]
{{col-end}}

[[Critique of the Kantian philosophy|Criticism of Kant's system]] followed, firstly, by [[Arthur Schopenhauer]], who amongst other things was unhappy with the term "Community", and declared that the tables "do open violence to truth, treating it as nature was treated by old-fashioned gardeners",<ref>Schopenhauer A. ''The World as Will and Representation'' (tr. Payne A., Dover Publications, London, New York, 1966) p.430</ref> and secondly, by [[Walter Terence Stace|W.T.Stace]] who in his book ''The Philosophy of Hegel'' suggested that in order to make Kant's structure completely symmetrical a third category would need to be added to the Mathematical and the Dynamical.<ref>''Op.cit.15'' p.222</ref> This, he said, Hegel was to do with his category of concept.

===Hegel===
[[Georg Wilhelm Friedrich Hegel|G.W.F. Hegel]] in his ''[[Science of Logic]]'' (1812) attempted to provide a more comprehensive system of categories than Kant and developed a structure that was almost entirely triadic.<ref>''Ibid.''</ref> So important were the categories to Hegel that he claimed the first principle of the world, which he called the "[[Absolute spirit|absolute]]", is "a system of categories&nbsp;{{omission}} the categories must be the reason of which the world is a consequent".<ref>''Ibid.'' pp.63,65</ref>

Using his own logical method of [[Aufheben|sublation]], later called the [[Hegelian dialectic]], reasoning from the abstract through the negative to the concrete, he arrived at a hierarchy of some 270 categories, as explained by [[Walter Terence Stace|W.&nbsp;T.&nbsp;Stace]]. The three very highest categories were "logic", "nature" and "spirit". The three highest categories of "logic", however, he called "being", "essence", and "notion" which he explained as follows:

* Being was differentiated from Nothing by containing with it the concept of the "[[Other (philosophy)|other]]", an initial internal division that can be compared with Kant's category of disjunction. Stace called the category of Being the sphere of common sense containing concepts such as consciousness, sensation, quantity, quality and measure.
* [[Essence]]. The "other" separates itself from the "one" by a kind of motion, reflected in Hegel's first synthesis of "[[Becoming (philosophy)|becoming]]". For Stace this category represented the sphere of science containing within it firstly, the thing, its form and properties; secondly, cause, effect and reciprocity, and thirdly, the principles of classification, identity and difference. 
* [[Notion (philosophy)|Notion]]. Having passed over into the "Other" there is an almost [[Neoplatonism#Return to the One|neoplatonic return]] into a higher unity that in embracing the "one" and the "other" enables them to be considered together through their inherent qualities. This according to Stace is the sphere of philosophy proper where we find not only the three types of logical proposition: disjunctive, hypothetical, and categorical but also the three [[Transcendentals|transcendental concepts]] of beauty, goodness and truth.<ref>''Op.cit.18'' pp.124ff</ref>

[[Arthur Schopenhauer|Schopenhauer's]] category that corresponded with "notion" was that of "idea", which in his ''Four-Fold Root of Sufficient Reason'' he complemented with the category of the "will".<ref>''Op.cit.20''</ref> The title of his major work was ''[[The World as Will and Representation|The World as Will and Idea]]''. The two other complementary categories, reflecting one of Hegel's initial divisions, were those of Being and Becoming. At around the same time, [[Johann Wolfgang von Goethe|Goethe]] was developing his colour theories in the {{lang|de|[[Theory of Colours|Farbenlehre]]}} of 1810, and introduced similar principles of combination and complementation, symbolising, for Goethe, "the primordial relations which belong both to nature and vision".<ref>Goethe J.W. von, ''The Theory of Colours'' (tr. Eastlake C.L., MIT Press, Cambridge, Mass., 1970) p.350</ref> [[Georg Wilhelm Friedrich Hegel|Hegel]] in his ''[[Science of Logic]]'' accordingly asks us to see his system not as a tree but as a circle.

==Twentieth-century development==
In the twentieth century the primacy of the division between the subjective and the objective, or between mind and matter, was disputed by, among others, [[Bertrand Russell]]<ref>Russell B. ''The Analysis of Mind'' (George Allen & Unwin, London, 1921) pp.10,23</ref> and [[Gilbert Ryle]].<ref>Ryle G. ''The Concept of Mind''  (Penguin, Harmondsworth, 1949) pp.17ff</ref> Philosophy began to move away from the metaphysics of categorisation towards the linguistic problem of trying to differentiate between, and define, the words being used. [[Ludwig Wittgenstein]]’s conclusion was that there were no clear definitions which we can give to words and categories but only a "halo" or "corona"<ref>Wittgenstein L. ''Philosophical Investigations'' 1953 (tr. Anscombe G., Blackwell, Oxford, 1978) pp.1x

X
4,181</ref> of related meanings radiating around each term. Gilbert Ryle thought the problem could be seen in terms of dealing with "a galaxy of ideas" rather than a single idea, and suggested that [[category mistake]]s are made when a concept (e.g. "university"), understood as falling under one category (e.g. abstract idea), is used as though it falls under another (e.g. physical object).<ref>Ryle G. ''Collected Papers'' (Hutchinson, London, 1971) Vol.II: ''Philosophical Arguments'' 1945, pp.201,202</ref> With regard to the visual analogies being used, [[Charles Sanders Peirce|Peirce]] and [[Clarence Irving Lewis|Lewis]],<ref>''Op.cit.1'' pp.52,82,106</ref> just like [[Plotinus]] earlier,<ref>''Op.cit.9'' VI.5.5</ref> likened the terms of propositions to points, and the relations between the terms to lines. Peirce, taking this further, talked of univalent, bivalent and trivalent relations linking predicates to their subject and it is just the number and types of relation linking subject and predicate that determine the category into which a predicate might fall.<ref>''Op.cit.5'' Vol I pp.159,176</ref> Primary categories contain concepts where there is one dominant kind of relation to the subject. Secondary categories contain concepts where there are two dominant kinds of relation. Examples of the latter were given by [[Martin Heidegger|Heidegger]] in his two propositions "the house is on the creek" where the two dominant relations are spatial location (Disjunction) and cultural association (Inherence), and "the house is eighteenth century" where the two relations are temporal location (Causality) and cultural quality (Inherence).<ref>''Op.cit.4'' pp.62,187</ref> A third example may be inferred from Kant in the proposition "the house is impressive or [[Sublime (philosophy)|sublime]]" where the two relations are spatial or mathematical disposition (Disjunction) and dynamic or motive power (Causality).<ref>Kant I. ''Critique of Judgement'' 1790 (tr. Meredith J.C., Clarendon Press, Oxford 1952) p.94ff</ref> Both [[Charles Sanders Peirce|Peirce]] and [[Ludwig Wittgenstein|Wittgenstein]]<ref>''Op.cit.25'' pp.36,152</ref> introduced the analogy of [[colour theory]] in order to illustrate the shades of meanings of words. Primary categories, like primary colours, are analytical representing the furthest we can go in terms of analysis and abstraction and include Quantity, Motion and Quality. Secondary categories, like secondary colours, are synthetic and include concepts such as Substance, Community and Spirit. 

Apart from these, the categorial scheme of [[Alfred North Whitehead]] and his Process Philosophy, alongside [[Nicolai Hartmann]] and his Critical Realism, remain one of the most detailed and advanced systems in categorial research in metaphysics.

===Peirce===
{{main|Categories (Peirce)}}

[[Charles Sanders Peirce]], who had read Kant and Hegel closely, and who also had some knowledge of Aristotle, proposed a system of merely three phenomenological categories: [[Categories (Peirce)|Firstness, Secondness, and Thirdness]], which he repeatedly invoked in his subsequent writings. Like Hegel, C.S. Peirce attempted to develop a system of categories from a single indisputable principle, in Peirce's case the notion that in the first instance he could only be aware of his own ideas. 
	"It seems that the true categories of consciousness are first, feeling&nbsp;... second, a sense of resistance&nbsp;... and third, synthetic consciousness, or thought".<ref>''Op.cit.5'' p.200, cf Locke</ref>
	Elsewhere he called the three primary categories: [[Quality (philosophy)|Quality]], Reaction and [[Meaning (semiotics)|Meaning]], and even [[Categories (Peirce)|Firstness, Secondness and Thirdness]], saying, "perhaps it is not right to call these categories conceptions, they are so intangible that they are rather tones or tints upon conceptions":<ref>''Ibid.'' p.179</ref>     
*Firstness ([[Quality (philosophy)|Quality]]): "The first is predominant in feeling&nbsp;... we must think of a quality without parts, e.g. the colour of magenta&nbsp;... When I say it is a quality I do not mean that it "inheres" in a subject&nbsp;... The whole content of consciousness is made up of qualities of feeling, as truly as the whole of space is made up of points, or the whole of time by instants".
*Secondness (Reaction): "This is present even in such a rudimentary fragment of experience as a simple feeling&nbsp;... an action and reaction between our soul and the stimulus&nbsp;... The idea of second is predominant in the ideas of causation and of statical force&nbsp;... the real is active; we acknowledge it by calling it the actual".
*Thirdness ([[Meaning (semiotics)|Meaning]]): "Thirdness is essentially of a general nature&nbsp;... ideas in which thirdness predominate [include] the idea of a sign or representation&nbsp;... Every genuine triadic relation involves meaning&nbsp;... the idea of meaning is irreducible to those of quality and reaction&nbsp;... synthetical consciousness is the consciousness of a third or medium".<ref>''Ibid.'' pp.148-179</ref>

Although Peirce's three categories correspond to the three concepts of relation given in Kant's tables, the sequence is now reversed and follows that given by [[Science of Logic|Hegel]], and indeed before Hegel of the three moments of the world-process given by [[Neoplatonism|Plotinus]]. Later, Peirce gave a mathematical reason for there being three categories in that although monadic, dyadic and triadic nodes are irreducible, every node of a higher valency is reducible to a "compound of triadic relations".<ref>''Ibid.'' p.176</ref> [[Ferdinand de Saussure]], who was developing "semiology" in France just as Peirce was developing "semiotics" in the US, likened each term of a proposition to "the centre of a constellation, the point where other coordinate terms, the sum of which is indefinite, converge".<ref>Saussure F. de,''Course in General Linguistics'' 1916 (tr. Harris R., Duckworth, London, 1983) p.124</ref>

===Others===
[[Edmund Husserl]] (1962, 2000) wrote extensively about categorial systems as part of his [[Phenomenology (philosophy)|phenomenology]].<ref>{{Cite book |last=Husserl |first=Edmund |url=https://www.worldcat.org/oclc/45592852 |title=Logical investigations |date=2001 |others=J. N. Findlay, Michael Dummett, Dermot Moran |isbn=0-415-24189-8 |edition= |location=London |oclc=45592852}}</ref><ref>{{Cite book |last=Husserl |first=Edmund |url=https://www.worldcat.org/oclc/45592852 |title=Logical investigations |others=J. N. Findlay, Michael Dummett, Dermot Moran |isbn=0415241901 |oclc=45592852}}</ref>

For [[Gilbert Ryle]] (1949), a category (in particular a "[[category mistake]]") is an important semantic concept, but one having only loose affinities to an ontological category.<ref>{{Cite book |last=Ryle |first=Gilbert |url=https://www.worldcat.org/oclc/49901770 |title=The concept of mind |date=2002 |publisher=University of Chicago Press |isbn=0-226-73296-7 |edition= |location=Chicago |oclc=49901770}}</ref>

Contemporary systems of categories have been proposed by [[John G. Bennett]] (The Dramatic Universe, 4 vols., 1956–65),<ref>{{Cite book |last=Bennett |first=John G. |url=https://www.worldcat.org/oclc/18242460 |title=The dramatic universe |date=1987 |publisher=Claymont Communications |isbn=0-934254-15-X |location=Charles Town, W. Va. |oclc=18242460}}</ref> [[Wilfrid Sellars]] (1974),<ref>{{Citation |last=deVries |first=Willem |title=Wilfrid Sellars |date=2021 |url=https://plato.stanford.edu/archives/fall2021/entries/sellars/ |encyclopedia=The Stanford Encyclopedia of Philosophy |editor-last=Zalta |editor-first=Edward N. |edition=Fall 2021 |publisher=Metaphysics Research Lab, Stanford University |access-date=2022-07-15}}</ref> [[Reinhardt Grossmann]] (1983, 1992), Johansson (1989), Hoffman and Rosenkrantz (1994), [[Roderick Chisholm]] (1996), [[Barry Smith (ontologist)]] (2003), and [[E. J. Lowe (philosopher)|Jonathan Lowe]] (2006).

==See also==
{{div col|colwidth=22em}}
* [[Categories (Aristotle)]]
* [[Categories (Peirce)]]
* [[Categories (Stoic)]]
* [[Category (Kant)]]
* [[Metaphysics]]
* [[Modal logic]]
* [[Ontology]]
* [[Schema (Kant)]]
* [[Similarity (philosophy)]]
{{div col end}}

==References==
{{Reflist|30em}}

==Selected bibliography==

*[[Aristotle]], 1953. ''[https://web.archive.org/web/20051212140439/http://etext.library.adelaide.edu.au/a/aristotle/metaphysics/ Metaphysics]''. Ross, W. D., trans. Oxford University Press.
*--------, 2004. ''[http://etext.library.adelaide.edu.au/a/a8/categori.html Categories]'', [[Ella Mary Edghill|Edghill, E. M.]], trans. Uni. of Adelaide library.
*[[John G. Bennett]], 1956–1965. ''The Dramatic Universe''. London, Hodder & Stoughton.
*[[Gustav Bergmann]], 1992. ''New Foundations of Ontology''. Madison: Uni. of Wisconsin Press.
*Browning, Douglas, 1990. ''Ontology and the Practical Arena''. Pennsylvania State Uni.
*Butchvarov, Panayot, 1979. ''Being qua Being: A Theory of Identity, Existence, and Predication''. Indiana Uni. Press.
*[[Roderick Chisholm]], 1996. ''A Realistic Theory of Categories''. Cambridge Uni. Press.
*[[James Feibleman|Feibleman, James Kern]], 1951. ''Ontology''. The Johns Hopkins Press (reprinted 1968, Greenwood Press, Publishers, New York).
*Grossmann, Reinhardt, 1983. ''The Categorial Structure of the World''. Indiana Uni. Press.
*Grossmann, Reinhardt, 1992. ''The Existence of the World: An Introduction to Ontology''. Routledge.
*[[Leila Haaparanta|Haaparanta, Leila]] and Koskinen, Heikki J., 2012. ''Categories of Being: Essays on Metaphysics and Logic''. New York: Oxford University Press.
*Hoffman, J., and Rosenkrantz, G. S.,1994. ''Substance among other Categories''. Cambridge Uni. Press.
*[[Edmund Husserl]], 1962. ''Ideas: General Introduction to Pure Phenomenology''. Boyce Gibson, W. R., trans. Collier.
*------, 2000. ''Logical Investigations'', 2nd ed. Findlay, J. N., trans. Routledge.
*Johansson, Ingvar, 1989. ''Ontological Investigations''. Routledge, 2nd ed. Ontos Verlag 2004.
* [[Charles H. Kahn|Kahn, Charles H.]], 2009. ''Essays on Being'', Oxford University Press.
*[[Immanuel Kant]], 1998. ''Critique of Pure Reason''. Guyer, Paul, and Wood, A. W., trans. Cambridge Uni. Press.
*[[Charles Sanders Peirce]], 1992, 1998. ''[[Charles Sanders Peirce bibliography#EP|The Essential Peirce]]'', vols. 1,2. Houser, Nathan et al., eds. Indiana Uni. Press.
*[[Gilbert Ryle]], 1949. ''The Concept of Mind''. Uni. of Chicago Press.
*[[Wilfrid Sellars]], 1974, "Toward a Theory of the Categories" in ''Essays in Philosophy and Its History''. Reidel.
*[[Barry Smith (ontologist)|Barry Smith]], 2003. "Ontology" in ''Blackwell Guide to the Philosophy of Computing and Information''. Blackwell.

==External links==
{{EB1911 poster|Category}}
* Aristotle's ''[http://classics.mit.edu/Aristotle/categories.html Categories]'' at MIT.
* {{cite SEP |url-id=categories |title=Categories |last=Thomasson |first=Amie |author-link=Amie Thomasson}}
* "[http://ejap.louisiana.edu/EJAP/1997.spring/thomasson976.html Ontological Categories and How to Use Them]" – Amie Thomasson.
* "[http://www.cs.vassar.edu/~weltyc/fois/fois-2001/keynote/ Recent Advances in Metaphysics]" – E. J. Lowe.
* [http://www.ontology.co/ Theory and History of Ontology] – Raul Corazzon.

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[[Category:Concepts in metaphysics]]
[[Category:Philosophical categories|*]]