Aristotle's Theory of Movement and Cosmology

Aristotle's Theory of Movement and Change

The method that explains the change and movement of nature is the general theory of movement and change, where Aristotle distinguishes different types of change:

• Spatial Change: Movement which may be natural or violent.
• Growth
• Change in Quality: The alteration of the subject.
• Alteration
• Building
• Corruption

Natural and Violent Movement

Aristotle distinguishes two types of movement: natural movement, which is one in which beings tend to place themselves where they perfectly correspond to nature, and violent movement, which is one in which beings tend towards a place that does not belong to them, and therefore, a movement that has been caused by an agent.

The Structure of the Aristotelian Universe

The general theory is designed by Aristotle as the reason for the explanation of reality and movement; this movement includes the movement of planets (cosmology). He stated that the universe had 55 layers that compose the Aristotelian universe, which contains no empty space or vacuum (no separation between layer and layer), and each layer is composed of ether.

The Sublunar and Supralunar Worlds

In the first layer lies the moon. This whole region between the moon and Earth, which is the center of the universe, is the Sublunar world (where all processes of change and corruption occur). In the rest of the layers is the Supralunar world, a world where everything is perfect and eternal (no generation or corruption), in which the stars remain forever, and so does their movement.

The Unmoved Mover

The last layer is the limit of the universe, and beyond that layer is the engine (the Unmoved Mover) that is perfect and moves everything without anything causing it to move. For Aristotle, rest is the natural state of things.

Explaining Perfect and Imperfect Movements

If there is movement, we must explain whether it is perfect or imperfect based on how it is produced. We must explain the origin of perfect movements, which are the movements of the planets (they follow a perfect path, but they are not at rest). It also explains the origin of imperfect movements produced in the Sublunar world (the movement of the sun, the seasons, birth, death, and growth). If the motion is determined by the flawed Sublunar world, it is because the movement is transferred from the movement caused by the perfect sun.