Plato’s Theory of Forms.
Plato’s Theory of Forms or Theory of Ideas, holds that forms (the abstract quality or property of something) exist independent of Space and Time. It asserts that non-material abstract (but substantial) forms (or ideas), and not the material world of change known to us through sensation, possess the highest and most fundamental kind of Reality.

Forms are:

Transcendent – the forms are not located in Space and Time. For example, there is no particular place or time at which redness exists.

Pure – the forms only exemplify one property. Material objects are impure; they combine a number of properties such as blackness, circularity, and hardness into one object. A form, such as circularity, only exemplifies one property.

Archetypes – the forms are archetypes; that is, they are perfect examples of the property that they exemplify. The forms are the perfect models upon which all material objects are based. The form of redness, for example, is red, and all red objects are simply imperfect, impure copies of this perfect form of redness.

Ultimately Real – the forms are the ultimately real entities, not material objects. All material objects are copies or images of some collection of forms; their Reality comes only from the forms.

Causes – the forms are the causes of all things. They provide the explanation of why any thing is the way it is, and they are the source or origin of the being of all things.

Systematically Interconnected – the forms comprise a system leading down from the form of the good moving from more general to more particular, from more objective to more subjective. This systematic structure is reflected in the structure of the dialectic process by which we come to knowledge of the forms.
Twiggie 2016