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Volume III

Platonic Realism in the Categories

by Amer Amer

I.  Historical Context and Motivation


Diogenes Laertius tells a story of a public reading of the Phaedo given by Plato.  This lecture is said to have not been a public success and people gradually slipped away, until it was only Aristotle that remained through to the end.  It is widely accepted that Aristotle entered the Academy at the age of seventeen, and studied there for the better part of twenty years, only leaving upon Plato’s death.  In this time, he would have been exposed to the later works of Plato, including the Timaeus and the Philebus.  More importantly for this discussion, however, Aristotle would have been exposed to the Phaedo, one of the first texts in which Plato develops a “Theory of Forms,” addressing the important philosophical question of “why are things the way they are?”  It is also likely that Aristotle was exposed to teachings that were transmitted only orally (as Plato harshly criticizes all written transmission of epistémé in the Phaedrus).  With regard to his own work, some scholars have considered the Categories one of Aristotle’s earlier works, as it lacks the material/formal distinction that is otherwise consistently central within his philosophy.  On this basis, a cross-examination of the Categories with the Phaedo provides insight into the fascinating interpretational puzzle of knowing whether the younger Aristotle preserves or rejects Platonic doctrine—and the Pythagorean tradition altogether.  Furthermore, the Phaedo in particular is a great introduction to the intellectual challenges that Aristotle must have faced in the Academy, notably in its stimulation of Aristotle’s “Doctrine of the Causes,” for example.  It is important to note that this puzzle cannot be fully solved without taking into account the remaining evidence of Aristotle’s published (lost) dialogue Protrepticus.  However, since this is an obscure zone of scholarship with which I have yet to sufficiently engage, I will be concentrating on the evidence in surviving works, particularly that of the Categories, a work that Aristotle prepared for students in his Lyceum, whom already had an understanding of where Aristotle’s thought differed from Plato’s.  

II.  Preliminary


This study of the Categories investigates the extent to which the text can be interpreted as Nominalist or Realist.  This lens of inquiry occupied medieval and scholastic thinkers and for this reason might seem to be superimposed here onto the earlier documents in question.  However, the terms in which I examine this issue are not anachronistic.  In fact, Plato himself lays the ground for this debate in the opening philosophical conversation of the Parmenides, preceding the central dialectical gymnastics.  It is for this reason that the outcome of this Nominalist-Realist deliberation affords a rich discussion of whether this text is more or less inline with Platonic tradition, which is the primary inquiry of this paper.  It is my contention that the text warrants a strong Platonic Realist reading, on the grounds that Aristotle (1) insists that essential universals are ‘Secondary Substances’ and (2) that essences and differentiae cannot be mind-dependent.  Furthermore, although there is a fundamental conflict between the Platonic and Aristotelian notions of essence, a Platonic reading remains defensible primarily due to the text’s deliberate lack of any material/formal distinction.  


This thesis will be presented as follows: First, a summary of the “Four-Fold Distinction” will be provided so that the subject of investigation is adequately situated in the broader scheme of the text.  Second, the Nominalist account will be provided, supported with references to a Nominalist reading by M. J. Cresswell.  Third, the Realist account will be provided, supported with references to a Realist reading by David Henry.  Fourth, a brief summary of Realism in Platonism (limited to that of Plato’s Phaedo) will be provided, followed by a discussion of whether the Platonic and Aristotelian notions of essence are compatible.  Fifth, an argument for the Realist interpretation of the Categories will be presented.  Finally, a discussion of the consistencies and inconsistencies of the Platonic reading of the Categories is presented, which connects the discussion of substance in the Categories to the development of Aristotelian substance theory in the Metaphysics.  This essay assumes that the sequencing of Aristotle’s texts is correct and that it is licit that they be used to interpret each other.

III.  The ‘Four-Fold Distinction’


In the Categories, ‘secondary substances’ are conceptualized as part of a complete system of subject classification.  Predication is the principle of this categorical division, which has come to be known by scholars as the “Four-Fold Distinction.”  In this text, Aristotle differentiates between two types of predication: said of predications, which predicate both the name and definition of a subject; and in predications, which never predicate definition, but occasionally predicate the name of a subject.   For Aristotle, a definition is a singular denotation of what is required for a subject to be ‘what it is.’  Consequently, said of predications are referred to as ‘essential’, and in predications as ‘accidental,’ due to the latter connotating no definition.  In other words, the addition or subtraction of an accidental predicate has no effect in altering the identity of the subject of its predication, as identity persists independently of accidentals.  


On this basis, Aristotle distinguishes four categorical classes: (1) ‘Non-substance particulars’ (as ‘accidental’): predicates that are not said of but present in other subjects; (2) ‘Non-substance universals’ (as ‘essential’): predicates said of and present in other subjects; (3) ‘Individual substances:’ designated as ‘primary substances’ because they are neither essential to another’s being nor accidentally in other beings; (4) ‘Universal substances’ (as ‘essential’): said of but not present in other (primary) substances.  From this, it follows that ‘universal substances’ are deemed ‘secondary substances’ precisely because they “reveal the primary substance” by being said of them, i.e., by predicating their essences.  However, there is ambiguity here about the way in which primary and secondary substances interact, and the nature of their relationship, which generates interpretational disagreement between conflicting Nominalist and Realist scholars: it is unclear whether Aristotle intends this system to apply purely as a science of logic, which is concerned only with correct application of the logical structure and semantics of rational agents, or whether he intended for the system to function as a procedure for empirical science and ontology’s interactions with the external world, which contains distinct material and formal aspects.  Additionally, there is disagreement as to whether or not the “Four-Fold Distinction” is conceptually exhaustive, and whether it ought to be understood as an alternative to, or supplement for, Plato’s Form-based theory of substance-hood.  There is no unanimity amongst the scholars that engage in this debate, hence, this dialectic will provide the basis of discussion for this paper.  


IV.  Nominalism


Nominalism, in this context, rejects the external existence of universals, maintaining that the only things that exist external to us are particulars.  Universals like ‘animals’ are mere names, designations of sets of concrete particular objects.  These designations extrapolated from observing ‘biological kinds’ and are merely conceptual, “the actual existence of which is mind-dependent.”  As I understand it, the concept of ‘mind-dependent’ holds universals to be the result of the subject-predications in the minds of rational beings.  Furthermore, it is in the rational being’s nature to project distinctions upon studying differentia in individual substances and categorizing commonalities.  This is analogous to the dependence of knowledge on the existence of minds.  The Nominalist view promotes a reading of the Categories in which the categorical division, of which I spoke about earlier, is deemed a theoretical categorization of subjects of predication, one established by rational animals, which is also non-reflective of nature.  


Cresswell offers a Nominalist reading of the Categories where “the meaning of universal terms can be explained in terms of non-universal pointables,” a view he grounds in the Aristotelian notion of ‘specific identity,’ such that belonging to a particular class of beings is to be identical to the members of a species.  Cresswell describes his view as “the primitive logical notion of specific identity” which allows us “to define a class by means of a pointable thing, assuming that the members of the class are pointable things.”  Cresswell appeals to the notion of ‘ostensive’ or ‘extensive’ definition, a concept in the semantics of predicate logic wherein a definitional meaning is captured by ‘pointing out’ examples in the world.  This is contrasted with the notion of  ‘intensive’ definition, a language-based dictionary definition.  This ‘pointing’, Cresswell maintains, “need not be thought of as a physical pointing” and that “the metaphysical talk can be made precise if we think of a theory of universals as set out in the language of first-order predicate logic.”  This interpretation of the theory of universals is formalized “in a first-order language containing … only finitely many predicates” bound by “infinitely many individual constants.”  In this view, the answer to the question ‘what it is’ requires one to be able to identify one of the primary substances of a class, such that to be X is to be ‘specifically identical’ with X.  Cresswell maintains that “equivalence classes” are species, and that the term ‘specific identity’ is a reference to the attributes that all members of a species share in common.  Therefore, a universal is an idea that abstracts the essential characteristics that specific primary substances share within their class.  Cresswell concludes that “we do not find a theory of universals in Aristotle because Aristotle did not see a problem of universals,” meaning that Aristotle did not have a problem understanding how one thing could be many.  The immediate implication here is that Aristotle allows for the sharing of identity between particular subjects insofar as they all belonged to a larger unit, in this case, to a biological class.  However, this thought can be seen as strongly Platonic; insofar as uniqueness of identity is incrementally lost, the closer a particular comes to that from which it receives its essence.  This is discussed at length in Section VI.  


Moreover, if a Nominalist interpretation of the text is to be plausible it must be capable of explaining how mind-dependent secondary substances can give essence to primary substances, which are real metaphysical objects.  The Nominalist’s way of understanding this is to make the process of essence-predication epistemological, such that one must know the universal to identify the individual, as it is the secondary substance that explains the ‘why it is’ of a subject.  This reading regards essence purely as the object of understanding.  Importantly, Aristotle maintains that primary substances are the basic subjects of which everything is predicated, constituting our ability to perform scientific inquiry.  Aristotle defines “science” as a process of attaining understanding, and “understanding” as knowing “the explanation because of which the object is ... and that it is not possible to be otherwise.”  Hence, insofar as primary substances are the subjects of scientific inquiry, a secondary substance predication is the scientific ‘definitional’ explanation of a primary substance, without which primary substances would not be understood.  Ontologically, an understanding of what a subject ‘is’ is not necessary to the subject’s existence, since primary substances already exist actually and do not require secondary substances for their being.  However, understanding essence is necessary for scientific knowledge because it reveals what is necessary for the primary subject’s existence.  This raises a concern that if universals are only epistemological phenomena, then it could be posited that essences do not exist in nature, but are only established in the mind.  For example, if we hold that ‘rationality’ is what makes an anthropos unique from any other animal (i.e., is the essence of this species), then the assertion that essences do not exist in nature restricts all claims that exercising this characteristic activity will allow for its class-specific excellence to be derived, and so for it’s specific eudaimonia to be attained.  This is because the possibility of asserting a larger world system that connects essence-predication to personal fulfillment, one that regulates itself independently of the particulars it contains, is restricted.  If essence is only a predication from the mind, then ‘purpose’ is made contingent to the accidental discovery of patterns.  Indeed, all essence would die with the mind.  Whether this view of essence is compatible with Aristotle’s worldview will be discussed in Section VII of the essay.  

V.  Realism


Realism, in this context, maintains that universals are not mere names but are naturally occurring substances that exist outside, and independent of, thought.  Furthermore, universals are responsible for predicating the essences of primary substances, meaning that they are capable of causal interaction.  Ellis defines Realism as “a mind-independent reality; that consists fundamentally of physical objects that have causal powers.”  The Realist view promotes a reading of the Categories in which it is stated: “some correct metaphysically privileged list of mind-and-language-independent highest kinds as well as a correct account of the relations between them.”  Henry offers a reading in which Aristotle is “committed to Realism”, because “the kinds from which the inquirer selects are natural kinds delineated by objective, mind-independent boundaries.”  Henry maintains that “sharing certain objective properties in common” and having “essence” are what establish ‘kinds’ as natural.  For Henry, the basis for a Realist reading is Aristotle’s interest in “general kinds”, in which are found “groups that (1) share a ‘single common nature’ and (2) contain ‘forms that are not too distant’.”  He maintains that the second condition has to do with “a distinction between higher-level kinds … which are divisible into forms, and so called infinima species.”  Though his reading does not pertain to the Categories directly, its argument for essences as forms, and forms as distinguishing classes, allows for a powerful argument for Realism in the Categories.  This will be returned to in Section VII of the essay, in which an argument for Realism in the Categories will be presented.  


If a Realist interpretation of the text is to be plausible, however, it must be compatible with the idea that the existence of secondary substances depends on that of primary substances.  Aristotle plainly maintains that if all individual cases of a certain secondary substance disappear, the secondary substance will cease to be as well, “if the primary substance did not exist it would impossible for any of the other things to exist.”  Nonetheless, a discussion concerning the extent of Platonism in the Categories is required before addressing this challenge.  

VI.  Realism in the Phaedo and a Comparison of Essences


The Phaedo is the Platonic dialogue primarily concerned with the question of the immortality of the soul.  However, the dialogue’s conclusions on the soul are dependent on the existence of purely intelligible, universal and unchangeable entities identified as Forms, which perform two explanatory functions: First, in what is referred to as the “Recollection Argument,” Plato states that learning is a matter of the soul’s recollection of the intelligible realm of Forms, a process triggered by interaction with sensible objects, thereby limiting the process of understanding to re-familiarizing with the abstract universals that exist in reality (albeit in a separate realm).  Plato’s assertion that the soul comes in contact with the Forms prior to embodiment establishes his philosophy as Realistic, since the Forms exist externally and independently of rational agents.  Second, in the latter portion of the dialogue, Plato posits an account of how things are what they are by virtue of their partaking in the Forms, thus attributing to the Forms the capacity to explain the existence of beings and objects in the sensible world.  The account of the Forms in the Phaedo maintains that the ‘being’ of the sensible is dependent on the existence of Forms.  Though particulars are ‘what they are’ in virtue of partaking in the Forms, Forms have no requirement that ‘sensibles’ partake in them, in any way.  This ontological asymmetry establishes the Forms as logically prior to particulars, since their subsistence is independent of particulars.


If partaking means that some Form is essentially part of the particular, then the relationship is synonymous in that both the name and the definition are attributed to the primary substance, making for a kind of Aristotelian Platonism.  However, if in participating in the Forms, what is meant is that the particular only resembles the Form, and that there is no essence within the particular, then the relationship would be homonymous in that the particular and the Form only share a name in common, if not paronymously, and is thus in conflict with Aristotelian substance theory.  The essence-predication view is upheld here, as follows: Insofar as ‘essence’ is something without which another subject cannot be what it is, particulars maintain essential-relations with Forms because they provide the explanation for what something is.  However, this requires Plato to either posit a Form for everything in order to explain the being of all particulars, which he is against, or to differentiate between things that do and do not require Forms for explanation.  As will be discussed in Section VIII, this is one of Aristotle’s reasons for rejecting the “Doctrine of the Forms.”  


Both philosophers consider their philosophies as answering the question of ‘what it is.’  However, their understanding of ‘what it is’ explanations (hence essences) are inherently different.  Cresswell describes the Phaedo account of essence relations between Forms and particulars as “identity in respect of” such that the answer to the question ‘what it is’ is that something’s identity is relative to some Form.  For Plato, ‘Socrates is man’ and ‘Socrates is wise’ are equally relations to Forms, not differentiating between essential and accidental predications, resulting in both ‘man’ and ‘wisdom’ being equal substance universals.  Aristotle, on the other hand maintains that attributing something to a Form does not contain understanding and that the partaking-relations of Forms with particulars only predicate names, but not definitions.  Therefore, under Aristotle’s view, Forms do not predicate essence at all.  There is a clear substance and non-substance division in Aristotle’s Categories, in which, Socrates’ wisdom is due to his man-ness, insofar as this accidental property is in him due to his rational capacity, which is essential to his being a man, differentiating him from other species of a genus.  This puts Aristotelian essence in direct conflict with the essence-view of the Phaedo.  


Additionally, Platonic Forms are never presented as themselves existing on different ontological levels in the Phaedo.  In the Categories, Aristotle maintains that among secondary substances, some are more substance than others, “the species is more a substance than the genus, since it is nearer to the primary substance.”  Insofar as secondary substances are explanatory, scientific categorization (as opposed to the mathematical categorization in later Platonic Form-theory) regards the degrees of separation that distinguish secondary substances as designated by predicability: “the species is predicated of the individual, the genus both of the species and the individual.”  Hence, the ‘what it is’ explanation provided by one secondary substance is often predicated by a more abstracted secondary substance (genus).  This results in many essential predications of a primary substance as opposed to one essential relation to a Form.  


While there is a conflict between the Platonic and Aristotelian notions of essential identity and predication, it is not required that the conflict remove the possibility of maintaining a Platonic view of the Categories.  This is so because both views permit essential relations, despite having different understandings of what constitutes ‘essence.’  The current essay resolves that the two notions of essence are incompatible, however, I maintain that the conflict does not remove the possibility for an experimental Aristotelian-Platonism, a notion that will be discussed in Section VIII of the essay.  

VII.  Argument for Realism


With regards to the Realist and Nominalist debate, this essay supports a Realist reading of the Categories, for the following reasons: First, it is clear that Aristotle holds that essential universals are substance and that they “reveal” primary substance.  Therefore, a Nominalist reading would also have to maintain that primary substances are also mind-dependent, to avoid requiring two differing notions of substance, since the nature of substance in universals is regarded by the Nominalist as mind-dependent.  It is implausible that primary substances can be mind-dependent, due to the required existence of metaphysically real rational agents capable of projecting epistemological distinctions in the first place.  


Second, because Aristotle maintains that primary substances receive their essence from secondary substances, the Realist reading allows for a notion of essence that is more consistent with a material/formal understanding of nature, while not prohibiting a theory of epistemology.  It is a more plausible reading that essences are not mind-dependent, especially if the Physics is to be taken into account, because forms are essences as well as actual.  If forms did not exist in nature there would be no means by which a rational animal can project epistemological distinctions, e.g., there would be no way of making material distinctions, since any such distinction presupposes shape or structure (morphé).  Furthermore, it is because human understanding involves interaction with the world that we would be unable to identify ourselves as separate from other entities, or exercise the induction necessary for understanding (i.e., distinguishing universals, insofar as knowledge is contained in them, and induction is the first stage of understanding), “it is necessary for us to become familiar with the primitives by induction; for perception too instills the universal in this way.”  Therefore, a Nominalist view could not be upheld because essences must exist actually for anything that has material potentiality (including all primary substances) to come into being, but also to be capable of being thought or understood at all. It is interesting to note that though Aristotelian epistemology explicitly involves induction as a first step, it is not inconsistent with Platonic epistemology involves interaction with ‘sensibles’ as the first step in the process of Form recollection, as discussed in Section VI.  


Third, the Realist account avoids the Nominalist circularity with regards to differentiae.  Differentiae are attributes that distinguish both individuals from each other and species from genus.   Though differentia are essential, they are not substances.  Insofar as they are essential, however, following the same line of reasoning as in the argument above, differentia would also need to exist external to mind in order to allow any substantive distinction.  

VIII.  Inconsistency as a Testament to Plato


In the Categories, there is a Platonic position that regards the relationship between particulars and universals as one of essence-predication, but also regards universals as having immaterial existence in reality.  However, there is a clear anti-Platonic “commitment to the priority of individual substance to the kinds to which they belong” in the Categories.  Therefore, when both supported claims are combined, one is left with a concerning ‘inconsistency’, namely: That which gives essence depends on that which receives essence for its own being.  In this text, Aristotle seems to principally disagree with Plato on the ontological independence of universals from particulars.  This is an important challenge that any Platonic reading of Aristotle must necessarily confront.  Taking into consideration that this is an earlier work (assuming that our chronological placement of the texts is correct), I maintain that there is strength in interpreting ‘Aristotle the student’ as attempting to make the Platonic teachings compatible with his own observations of the world, a truly inspiring and empowering display of philosophical growth that speaks to Plato’s influence as a teacher and demand from his students.  Within this context, I view the Platonism of the Categories as an experimental Aristotelian-Platonism, or a “Platonism without the Forms” as Rist suggests.  It is experimental insofar as Aristotle’s intention was to account for the ways in which universals can exist within particulars, providing an explanation for how secondary substances could exist independently of matter.  Secondary substances are themselves immaterial in that they do not have material parts, though they are necessarily enmattered, i.e. non-material but dependent on material substances for their being.  That Aristotle was unsatisfied with the “Theory of Forms” is evident in his critique of this doctrine in the Metaphysics and the Nicomachean Ethics.  A central concern, in this regard, was the inability of the Forms to support a sufficiently scientific enterprise, one he viewed as necessary for understanding.  Therefore, since the Platonic Realist reading of the Categories is supported here, an argument for interpreting Aristotle as an expander of Plato’s thought, as one of the few to have direct access to Plato in his last years, must be provided.  


I maintain that the basis of this argument is precisely Aristotle’s lack of reference to any form/matter distinction in the Categories.  Had the “Four-Fold Distinction” been presented within the context of the Physics, assuming that Aristotle is true to any scientific and systematic method, his next step would be to contemplate whether secondary substances are purely formal or if there is a particular hylomorphic account that applies to them: “The salient feature of the Categories is surely its commitment to the primacy of individuals, and Aristotle could no doubt have avoided this commitment without having to introduce form and matter had he been writing the Categories with the Metaphysics up his sleeve.”  To the contrary, the Categories particularly avoids a discussion of the relationship between matter and form, as Cohen states “the concept of matter, of course, plays no role in the Categories.”  I find it most plausible that the text’s attempt to develop a theory of substance-hood, without the complications of material/formal relations, is an indicator of thought within a Platonic framework, further strengthening the Platonic reading of the Categories.  


I regard the text’s inconsistency in its account of substance-hood as the result of a deliberate absence of discussion on the roles of matter and form in substances.  That there is an inconsistency in the Categories is evident from Aristotle’s return to these issues of substance-hood, particularly in Metaphysics Z.  Ultimately, though Aristotle is unsatisfied with Plato’s Forms, it is not the case that he abandoned the reasoning that founded their philosophical importance.  Indeed, when deliberating whether form or matter was ‘more nature’ (signifying priority or essentiality) in the Physics, he responded that “the form indeed is nature rather than the matter; for a thing is more properly said to be what it is when it exists in actuality than when it exists potentially.”  This, then, reverts to the superiority of essences (which come from secondary substances) against the main anti-Platonic position in the Categories, found amongst the many consistently Platonic assertions he makes within this text.  

To conclude, looking forward into future paths in philosophical research, such paths include a study of what a ‘Platonism without Forms’ entails, which requires a more comprehensive study of the evolution of essence-theory in Platonic philosophy outside of the Phaedo, and into explicitly self-critical texts such as the Parmenides.  Additionally, a study of the development of essence-predication within the hylomorphic framework, a major feature of Aristotelian philosophy, the priority of which is discussed even beyond the scope of the natural and logical works. 


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Translation.  Edited by Jonathan Barnes.  Princeton, NJ: Princeton University Press, 1995.  


Nicomachean Ethics.  Translated by W. D. Ross.  Collected in The Complete Works of Aristotle: The Revised

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