The Categories (2000) Informative Summary


Aristotle’s Categories, translated here by E.M. Edghill, lays out his foundational system of classification for all things that can be said to exist. He introduces the concept of categories as the highest genera, under which all other things can be placed. The work primarily focuses on “substance,” the core of being, which Aristotle distinguishes as either primary (individual entities) or secondary (species and genera).

The text then systematically examines other categories like quantity, relation, quality, action, and affection, elucidating their characteristics and how they relate to substance. Throughout, Aristotle utilizes examples and logical arguments to clarify his points, highlighting the importance of precise language and definition in philosophical inquiry.

Key Findings:

  • Substance as the ultimate reality: Aristotle posits that individual things (primary substances) are the most real entities, with species and genera (secondary substances) being less real but still signifying essential aspects of being.
  • The importance of definition: Precise definitions are crucial for understanding the nature of things, particularly for distinguishing between categories and understanding relationships between them.
  • Distinction between primary and secondary substances: This distinction highlights the difference between individual entities and the universal concepts we use to understand them.
  • The role of contraries in understanding categories: Examining contraries helps define the limits and possibilities within each category, particularly evident in the discussions of quality and motion.


  • Understanding Categories: The reader will learn about Aristotle’s system of ten categories, which are the fundamental building blocks of knowledge and existence. These categories help us organize our thoughts and understand the world around us.
  • Nature of Substance: The text explains the concept of substance as the primary mode of being, differentiating between individual entities and the species and genera they belong to.
  • Importance of Logic and Language: Aristotle’s emphasis on clear definitions and logical deductions showcases the importance of precise language in philosophical inquiry, a principle applicable to any field requiring rigorous analysis.
  • The Interrelation of Categories: The text demonstrates how different categories relate to each other, emphasizing the interconnectedness of various aspects of existence.

Historical Context:

  • Ancient Greek Philosophy: This work is a product of Ancient Greek thought, reflecting the emphasis on logic, observation, and categorization that characterized this period.
  • Aristotle’s Influence: As one of the most influential philosophers in history, Aristotle’s Categories has shaped Western intellectual tradition significantly, impacting fields like logic, metaphysics, and science.


  1. Substance cannot be present in a subject: Primary substances, like a particular man, are not part of something else. Secondary substances, like “man” or “animal,” are predicated of a subject but not present in them.
  2. Everything except primary substances is either predicable of or present in a primary substance: Attributes like “white” or “running” are either predicated of a primary substance (a white horse) or present in it (the whiteness of the horse).
  3. Species is more truly substance than the genus: The species (man) is closer to the individual than the genus (animal) and provides a more informative description.
  4. Substance has no contrary: There’s no opposite to an individual man or the concept of “man.”
  5. Substance does not admit of variation of degree: A man cannot be “more” or “less” of a man at any given time.
  6. Quantity can be either discrete or continuous: Discrete quantities, like numbers, have distinct parts, while continuous quantities, like lines, have parts that join at a common boundary.
  7. Relatives are explained by reference to something else: Terms like “double” or “master” only make sense in relation to their correlatives.
  8. Correlatives come into existence simultaneously (for the most part): The existence of a master implies the existence of a slave, and vice versa.
  9. No substance is relative: Substances exist independently and are not defined by their relation to something else.
  10. Quality is that in virtue of which people are said to be such and such: It explains attributes like “white,” “grammatical,” or “just.”
  11. Habits are more lasting and firmly established than dispositions: Knowledge is a habit, while being hot is a disposition.
  12. Affective qualities are capable of producing an “affection” in the way of perception: Sweetness affects the sense of taste.
  13. One quality may be the contrary of another: Justice is the contrary of injustice.
  14. Qualities admit of variation of degree (generally): One thing can be whiter than another.
  15. Only qualities can be predicated with likeness and unlikeness: One thing can be similar or dissimilar to another based on their qualities.
  16. Action and affection both admit of contraries and variation of degree: Heating is the contrary of cooling.
  17. Rest is the contrary of motion: Different types of motion, such as generation and destruction, have their own specific contraries.
  18. Things are said to be opposed in four senses: Correlatives, Contraries, Privations & Positives, and Affirmatives & Negatives.
  19. Contrary attributes must needs be present in subjects which belong to the same species or genus: Health and disease both relate to the body.
  20. The term ‘to have’ is used in various senses: It can refer to possessing a quality, quantity, apparel, a part, content, or something acquired.


Aristotle’s Categories doesn’t rely on statistical data. The focus is on philosophical analysis and categorization using logic and examples rather than numerical figures.


  1. Substance: The essence of a thing, that which exists independently.
  2. Quantity: A measure of something, such as size, number, or extent.
  3. Quality: A characteristic or attribute of something, such as color, shape, or disposition.
  4. Relation: How one thing stands in comparison or connection to another.
  5. Action: The exertion of power or influence by one thing on another.
  6. Affection: A state of being acted upon or influenced by something else.
  7. Category: A fundamental classification of being or thought.
  8. Contrary: Two things that are diametrically opposed to each other.
  9. Privation: The absence or lack of something that is normally present.
  10. Relative: Something that is defined or understood in relation to something else.


  1. Man and Horse (Substance): Used to illustrate primary substances, individual entities that exist independently.
  2. White and Black (Quality): Examples of contrary qualities, demonstrating how one quality can be understood as the opposite of another.
  3. Double and Half (Relation): Used to explain correlatives, where one term’s existence is inherently linked to the other.
  4. Blindness and Sight (Privation and Positive): Sight is a positive quality of the eye; blindness is the privation of that quality.
  5. Heating and Cooling (Action and Affection): Heating is an action that causes something to become hot; being heated is the affection.
  6. Two Cubits Long (Quantity): An example of a definite quantity, used to explain that quantities like this have no contraries.
  7. Master and Slave (Relative): Illustrate how some terms only have meaning in relation to another term.
  8. Knowledge of Grammar (Habit): An example of a habit, a quality acquired through learning and practice that is enduring and difficult to change.
  9. Becoming Ashamed (Affection): Illustrates how affections are temporary states caused by external or internal factors.
  10. “He is sitting” (Affirmation) and “He is not sitting” (Negation): Demonstrate how these opposites are mutually exclusive, with one being true and the other false.


Aristotle’s Categories provides a framework for understanding the fundamental building blocks of existence and thought. By carefully defining categories like substance, quantity, relation, and quality, Aristotle emphasizes the importance of precise language and logical analysis in philosophical inquiry. The text also highlights the interconnectedness of these categories, showcasing how they work together to create a comprehensive understanding of the world. The enduring legacy of Categories is evident in its influence on Western intellectual history, shaping fields from metaphysics to linguistics.

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