The classical Greek philosophy is called rationalism. They theorized that the operation of the universe followed certain natural laws and that generalizations could therefore be made about the relationship of form and function.
Aristotle understood :
- homologous and analogous parts
- the function of different organs/systems
- how organs/systems vary among animals
- the relative perfection of organs/systems
- how some organs/systems relate to other organs/systems
He thought that the form of an animal was the result of some unknown cause or purpose, and he emphasized the plasticity of shape in service to function.
Homologous bones are shaded. From left to right: horse, human, whale, crocodile, bird.