Abstractionism is the theory that the mind obtains some or all of its concepts by abstracting them from concepts it already has, or from experience. One may, for example, abstract 'green' from a set of experiences which involve green along with other properties. Also, for example, one may abstract a generic concept like 'vegetable' from the already possessed concepts of its instances (carrot, broccoli, onion, etc.). This view was criticized by George Berkeley and Peter Geach.