How did Aristotle’s theory of matter and form differ from Democritus’s atomism?

Aristotle’s theory of hylomorphism and Democritus’s atomism represent fundamentally different approaches to explaining the nature of reality and change.

Democritus’s Atomism
Democritus proposed a mechanistic system where the universe consists solely of indivisible atoms moving in a void. In this view, all observable qualitative changes are merely the result of atoms rearranging, combining, or separating. Because the atoms themselves are immutable and possess only quantitative properties—such as size, shape, and motion—they are not subject to internal change. For Democritus, reality is reducible to these physical, unchanging corpuscles.123

Aristotle’s Hylomorphism
Aristotle rejected the concept of immutable atoms, arguing that the essence of matter is its capacity for change. His hylomorphic doctrine posits that every natural body is composed of two intrinsic, inseparable principles:
* Primary Matter: A potential, indeterminate principle.
* Substantial Form: An actual, determining principle.

Unlike atoms, which are physical entities, matter and form are metaphysical principles that cannot exist independently. Aristotle argued that for "becoming" or substantial change to occur, there must be a permanent, potential substrate (matter) that receives a new actualizing principle (form). He viewed the atomist claim of immutable ultimate realities as a contradiction, as it failed to account for the reality of change.425