“Categories” by Aristotle

Aristotle’s Foundational Works on Logic

The general categories enumerated herein have been widely accepted and used even at present, which speaks to Aristotle’s enormous influence on western civilization. His reasoning, however, is faulty in quite a few instances, especially with regard to the relation between genus and species.


Substance, quantity, quality, relation, place, time, position, state, action, or affection.

[–Update in 2014 –]

1. Substance

Substance, in the truest and primary sense of the word, is that which is neither predicable of a subject nor present in a subject (otherwise than as parts in a whole). In a secondary sense those things are called substances within which, as species, the primary substances are included, also those which, as genera, include the species. For instance, color is present in a body, but not predicable of it; animal is predicable of an individual man;

It is a distinctive mark of substance, that, while remaining numerically one and the same, it is capable of admitting contrary qualities, the modification taking place through a change in the substance itself.

2. Quantity

Quantity is either discrete or continuous. Instances of discrete quantities are number and vocal speech; of continuous, lines, surfaces, solids, and, time and place. Quantities consist either of parts which bear a relative position each to each, or of parts which do not. Spacial figures belong to the former, whereas speech, number, and time the latter.

Quantities have no contraries and do not admit of variation of degree. The most distinctive mark of quantity is that equality and inequality are predicated of it.

3. Relation
Relatives, which being either of something else or related to something else, are explained by reference to that other thing. For instance, superior, double, habit, disposition, perception, knowledge, and attitude (lying, standing and sitting). If relation to an external object is a necessary condition of existence for the relatives, then no substance is relative in character, e.g., a hand, which is part of a man, is not relative in character.

4. Quality

Quality is that in virtue of which people are said to be such and such. One sort of quality let us call ‘habit’ or ‘disposition’. Habit differs from disposition in being more lasting and more firmly established; Another sort of quality includes all those terms which refer to inborn capacity or incapacity; A third class within this category is that of affective qualities and affections, such as sweetness, bitterness, heat, and cold. The term ‘affective quality’ does not mean that those things which admit these qualities are affected in any way, but that these qualities are capable of producing an ‘affection’ in the way of perception. Those conditions, however, which arise from causes which may easily be rendered ineffective or speedily removed, are called, not qualities, but affections: for we are not said to be such virtue of them; The fourth sort of quality is figure and the shape that belongs to a thing; Rarity and density, roughness and smoothness really belong to a class different from that of quality. For it indicates a certain relative position of the parts composing the thing thus qualified.

Some qualities admit of variation of degree.

One thing is like or unlike another only with reference to that in virtue of which it is such and such; thus this forms the peculiar mark of quality.


Relatives, correlatives, contraries, variation of degree, privates vs. positives, affirmatives vs. negatives, genus and species, prior and posterior.

Prior and Posterior

There are four senses in which one thing can be said to be ‘prior’ to another: firstly, it has reference to time; secondly, one thing is said to be ‘prior’ to another when the sequence of their being cannot be reversed; thirdly, it is used with reference to any order, as in the case of science and of oratory (in sciences which use demonstration there is that which is prior and that which is posterior in order; in reading and writing, the letters of the alphabet are prior to the syllables, and in the case of speeches, the exordium is prior in order to the narrative); fourthly, that which is better and more honourable is said to have a natural priority; fifthly, in those things, the being of each of which implies that of the other, that which is in any way the cause may be said to be by nature ‘prior’ to the effect.



One thought on ““Categories” by Aristotle

  1. I appreciate this post, Nemo. I finished Categories feeling a bit confused as to what, exactly, Aristotle was trying to categorize and it’s relation to logic. This post makes things a little more clear.

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