Aristotle’s Categories of Being

In Aristotle’s book Categories in the Organon, Aristotle defines ten predicates of being, of which all one says of a thing can be classified as one of these ten categories.

In Aristotle’s book Categories in the Organon, Aristotle defines ten predicates of being, of which all one says of a thing can be classified as one of these ten categories. There is substance, or that which makes up the essence of a subject. The substance of a thing exists in itself and is not predicated of another. An example is ‘man’, or ‘horse’. Then there is the quality, which answers the question ‘What kind?’, and is the qualitative properties of the subject. An example is ‘blue’ or ‘oblong’. It exists in the substance. Then, there is quantity, which answers the question ‘how much?’, and some examples are ‘three gallons’ or ‘four years’. Next, there is relation, which describes a reference to another thing, or how something is related to another thing (for example, ‘double’, ‘half’, ‘father of’). The fifth category is place, defined as the location of an object in space (‘in the marketplace’, ‘ at home’). Next is time, or when something occurs or exists, or its temporal context (‘now’, ‘in 2020’, ‘yesterday’). The seventh term is position, which means the arrangement or posture of a thing (for instance, ‘sitting,’ ‘lying down,’ ‘standing’). Number eight states or condition a subject is in, such as ‘sick,’ ‘broken,’ or ‘cured.’ Next is action, which means what a subject is actively doing, like ‘running’, ‘standing’.Finally is passion, which means what a subject undergoes or is acted upon, for instance, ‘being burned’, ‘being cut’ (Aristotle 1960/4th Century B.C.E).

On Interpretation and the Foundations of Propositional Logic

Continuing the Aristotelian Organon is the book On Interpretation, in which Aristotle explores the semantic and logical structure of propositions. This includes the core notions of affirmation, negation, contrariness, and contradiction. These core concepts shall play a pivotal role in the development of propositional logic (Aristotle 1960/4th Century B.C.E). Whereas Aristotelian logic focused primarily on syllogisms, the advent of the Stoic movement in ancient Greece and Rome saw the rise of propositional logic. The Stoics developed a rudimentary form of propositional logic, using logical operators such as ‘if…’, ‘then…’, ‘either…’, and ‘or’. This alternative system emphasized the truth-value of entire statements, thus anticipating developments in the 19th and 20th centuries that we shall return to later (Mueller 1979).

Porphyry and the Five Predicables

Now, Porphyry expanded upon Aristotle’s logical system in late antiquity. Porphyr identified five predicables, or how a predicate is related to a subject. Among these five are species, or the specific kind or form of a thing, what it essentially is, and genus, which represents a general category under which multiple species fall. There is the differentia, which represents the characteristic that distinguishes one species from another within a genus. Then, there is property, which means a characteristic of a thing that is not part of the essence of that thing, but necessarily belongs to it. The final predicament is accident, which means a trait that may or may not apply to a subject, which plays no role in its essence (Porphyry, 1979/268-270). Let’s utilize Socrates as an example. The species of Socrates is human, the genus is animal. Now, what is the differentia that distinguishes the human from the other animals? Well, Aristotle argues it is the capacity to reason. Therefore, man is defined as a rational animal; a definition of a species therein consists of the differentia paired with a genus. An accident of Socrates will be heavy-set, as it is not necessarily part of his essence, and he would remain a human if he were not heavy.