Spinoza makes extensive use of the distinction between inconceivable things in the sense of things that we cannot conceive as real, existing things, and things that conceivably exist but in fact may or may not exist. About the latter, Spinoza says that they can be conceived, first, both to be and not to be and, second, to exist and not to exist. In addition, there are things (in the extremely broad sense of "thing") that cannot be conceived not to be. Things that are completely conceived through themselves cannot be conceived not to be. The way, and the only way, to conceive them is just to be confronted with them in the act of conception. They cannot be introduced into a discussion in the following way: "I shall now describe to you the essential properties of something, x, and let us then discuss whether it exists or not" (cf. IP8Sch2). If this kind of introduction were possible, this x would be conceivable by means of something else, namely, the description of a set of properties of x.