Form

Form, in the history of philosophy, term used to translate the Greek words idea and eidos, referring to a particular kind of entity which plays a prominent role in the philosophies of Plato and Aristotle.

Platonic forms are eternally existent, immaterial entities; they exist apart from the ordinary objects of experience in the sensible world around us; and they are the objects of reason rather than perception. Uncontroversial examples of Platonic forms include ethical and aesthetic properties, such as justice and beauty; properties of size, such as largeness and smallness; and geometrical properties, such as equality. Certain passages in Plato suggest an extension of the range of forms to include all properties that are common to many things. For Plato, forms are the proper object of philosophical inquiry since they, unlike the instances of these properties we perceive in the world around us, provide a stable basis for knowledge. Perceptible objects that have these properties, such as beautiful paintings or large buildings, are said to derive their beauty or largeness from their relation to the corresponding forms—beauty or largeness.

Whereas Platonic forms exist separately from the objects of ordinary experience, Aristotelian forms may be characterized as “immanent”: they do not exist over and above the objects which have them. The Aristotelian notion of form is tied to a correlative notion of matter. For example, bricks are the matter of which a house is composed. But the bricks, taken by themselves, do not constitute a house; they do so only by taking on the form of a house. For Aristotle, it is the form, more than the matter, which makes the house what it is; form constitutes the essence of the house as being a shelter for people and goods. In the case of artefacts, the form of each may be thought of as a certain functional shape. For Aristotle, however, the paradigm case of form is the form of a living thing, such as an animal or plant. This form is an internal dynamic principle which is causally responsible for the natural processes of development that the organism undergoes and which is reproduced in generation. Aristotle identifies the form of a living thing as its soul.

Although the term “form” is seldom used in modern philosophical discussion except in reference to Plato or Aristotle, their discussions of forms are the ancestors of much of the modern debate about universals, essence, and natural kinds, as well as of certain solutions to problems regarding the identity of objects over time.

See also Nominalism.