It is a common experience to observe that a particular painting—for example, a still life of apples—makes its subject “more real than it is in reality.” The apples seem brighter and firmer, they seem to possess an almost self-assertive character, a kind of heightened reality which neither their real-life models nor any color photograph can match. Yet if one examines them closely, one sees that no real-life apple ever looked like that. What is it, then, that the artist has done? He has created a visual abstraction.

He has performed the process of concept-formation—of isolating and integrating—but in exclusively visual terms. He has isolated the essential, distinguishing characteristics of apples, and integrated them into a single visual unit. He has brought the conceptual method of functioning to the operations of a single sense organ, the organ of sight.

No one can perceive literally and indiscriminately every accidental, inconsequential detail of every apple he happens to see; everyone perceives and remembers only some aspects, which are not necessarily the essential ones; most people carry in mind a vaguely approximate image of an apple’s appearance. The painting concretizes that image by means of visual essentials, which most men have not focused on or identified, but recognize at once. What they feel, in effect, is: “Yes, that’s how an apple looks to me!” In fact, no apple ever looked that way to them—only to the selectively focused eye of an artist. But, psycho-epistemologically, their sense of heightened reality is not an illusion: it comes from the greater clarity which the artist has given to their mental image. The painting has integrated the sum of their countless random impressions, and thus has brought order to the visual field of their experience.

- Ayn Rand. The Romantic Manifesto (1969).