Aristotle’s Metaphysics is one of the most influential philosophical works in history. It is a complex and multifaceted text that explores the nature of reality, existence, and being. However, if we were to identify one key feature of Aristotle’s Metaphysics, it would be his concept of substance.

What is Substance?

Substance, for Aristotle, refers to the fundamental essence of something. It is what makes a thing what it is and distinguishes it from everything else. For example, the substance of a tree is not its physical parts (leaves, branches, roots), but rather its essential nature as a living organism that grows from a seed into a full-grown plant.

The Four Causes

To understand Aristotle’s concept of substance better, we need to look at his theory of the four causes. According to Aristotle, there are four causes that explain why something exists and how it came to be:

For Aristotle, substance is closely related to the formal cause. It is the underlying form or structure that gives something its identity and determines how it behaves.

Primary and Secondary Substance

Aristotle makes a distinction between primary substance and secondary substance. Primary substance refers to individual things in the world – trees, animals, rocks – while secondary substances are categories or classes that these things belong to – plant, animal, mineral.

Primary substance:

Secondary substance:

Aristotle believes that primary substances are more real than secondary substances. They are the ultimate reality that exists independently of our thoughts and language. Secondary substances, on the other hand, are dependent on our mental categories and language conventions.

The Unmoved Mover

Aristotle’s concept of substance is closely related to his idea of the Unmoved Mover – an eternal, immaterial, and perfect being that is the ultimate cause and source of all motion in the universe. The Unmoved Mover is pure substance, without any material or accidental properties. It is the ultimate goal towards which everything in the world moves.


In conclusion, Aristotle’s Metaphysics is a complex work that covers many different topics and ideas. However, his concept of substance stands out as one of its key features.

Substance refers to the fundamental essence of something – what makes it what it is – and plays a crucial role in Aristotle’s theory of causation, ontology, and theology. By understanding Aristotle’s concept of substance, we can gain valuable insights into his philosophy as a whole and its enduring influence on Western thought.