Classical thinkers explored a more universal view of casually beyond the narrow limits of cause and effect.
In early times visible form was described as shape, appearance and idea. The Greek philosophers began to notice change in things and asked what the thing that changes really is. They called it substance meaning that which sands under the changes.
Form is a word specifying what a thing is, such as a statue or living forms such as a man, a dog, a cat, or an apple tree. Form is that which makes a thing be what it is. A statue such as the bust of Plato has shape which is its form but is not a the form of living Plato who could eat, run, work and think, therefore, there are different individualized forms.
Plato went a step forward and asking what a form was in itself. So, he came up with the theory of universal ideas or archetypes. For example, there are a variety of chairs styles but all have the same purpose. They are designed to sit in. The universal idea of chair takes on many specific shapes or forms. To Plato, the real was the universal idea which concrete objects were but shadows of the reality. "Plato describes the world of Forms as a pristine region of the physical universe located above the surface of the earth." In the Timaeus Plato wrote: "Since things are so, we must agree that that which keeps its own form unchangingly, which has not been brought into being and is not destroyed, which neither receives into itself anything else from anywhere else, nor itself enter into anything anywhere, is one thing."
To Plato these universal ideas always existed but where? This he did not see clearly. It was left to St. Thomas Aquinas to place these universal and eternal ideas into the mind of God. Unlike Plato, Aristotle retained the notion of form but viewed it as the intrinsic principle of a substance rather than the realized external prototype.