 When speaking of an existent mode—in this case, an actually occurring idea—Descartes will say that it possesses formal reality. The formal reality of a thing is the kind of reality the thing possesses in virtue of its being an actual or an existent thing (AT VII 41–42, 102–4; CSM II 28–29, 74–5). For example, given that the Sun is an actual or existent thing, it possesses formal reality. By contrast, given that Pegasus is not an actual or existent thing, he does not possess formal reality. Given that the idea of the Sun or the idea of Pegasus are actual or existent ideas, where an idea is actual or existent when it is being actively thought by a mind, each would possess formal reality. 