It is a commonplace that beauty lies in the eye of the beholder, but all the same we usefully talk of the beauty of things and people as if they are identifiable real properties which they possess. Projectivism denotes any view which sees us as similarly projecting upon the world what are in fact modifications of our own minds. The term is often associated with the view of sensations and particularly secondary qualities found in writers such as Hobbes (De Corpore, 1655) and Condillac (Traité des sensations, 1754). According to this view, sensations are displaced from their rightful place in the mind when we think of the world as coloured or noisy. Other examples of the idea involve things other than sensations, and do not involve literal displacement. One is that all contingency is a projection of our ignorance (Spinoza); another is that the causal order of events is a projection of our own mental confidences in the way they follow from one another (Hume). But the most common application of the idea is in ethics and aesthetics, where many writers have held that talk of the value or beauty of things is a projection of the attitudes we take towards them and the pleasure we take in them. The disadvantage of the metaphor of projection is that it makes it almost irresistible to suppose that if, for instance, we were not to disapprove of cruelty and project this as cruelty being wrong, then cruelty would not be wrong. And that in turn sounds unacceptable. So philosophers attracted to a sentimentalist account of such judgments have moved towards talking instead of expressivism.

It is natural to associate projectivism with the idea that we make some kind of mistake in talking and thinking as if the world contained the various features we describe it as having, when in reality it does not. But the view that we make no mistake, but simply adopt efficient linguistic expression for necessary ways of thinking, is also held. See also error theory, quasi-realism.