Aristotle

===== Immanent realism =====
{{Main|Aristotle's theory of universals}}
[[File:Platonic and Aristotelian Forms.svg| thumb | upright=1.5 | [[Plato]]'s [[Theory of forms|forms]] exist as [[universals]], like the ideal form of an apple. For Aristotle, both matter and form belong to the individual thing ([[hylomorphism]]).]]
Like his teacher Plato, Aristotle's philosophy aims at the [[Problem of universals|universal]]. Aristotle's [[ontology]] places the universal (''katholou'') in [[particular]]s (''kath' hekaston''), things in the world, whereas for Plato the universal is a separately existing form which actual things imitate. For Aristotle, "form" is still what [[phenomena]] are based on, but is "instantiated" in a particular substance.{{sfn| Cohen | 2000}}

Plato argued that all things have a [[Theory of forms|universal form]], which could be either a property or a relation to other things. When one looks at an apple, for example, one sees an apple, and one can also analyse a form of an apple. In this distinction, there is a particular apple and a universal form of an apple. Moreover, one can place an apple next to a book, so that one can speak of both the book and apple as being next to each other. Plato argued that there are some universal forms that are not a part of particular things. For example, it is possible that there is no particular good in existence, but "good" is still a proper universal form. Aristotle disagreed with Plato on this point, arguing that all universals are instantiated at some period of time, and that there are no universals that are unattached to existing things. In addition, Aristotle disagreed with Plato about the location of universals. Where Plato spoke of the forms as existing separately from the things that participate in them, Aristotle maintained that universals exist within each thing on which each universal is predicated. So, according to Aristotle, the form of apple exists within each apple, rather than in the world of the forms.{{sfn| Cohen | 2000}}{{sfn|Lloyd|1968|pages=43–47}}