In a cloud, the imagination can cut out patterns freely. The substance which fills them is real, but the objects which they outline do not exist. To exist, they would have to be distinguishable from the continuity within which they arose; they would have to constitute within it a particular and identifiable state endowed with an egregious privilege: duration. This duration can be brief or long, that of a cake of soap or of a spiral nebula; it is always of finite dimensions. This is what makes it the opposite of the instantaneousness of the mathematical beings which differential calculus arbitrarily cuts out within the continuity of movements.
Existence is a singularity that endures. But this duration, in the domain of the realities that are offered to our cognition, is never unlimited. In the universe of men there is nothing that escapes the slow or rapid, but always active, degradation which debases everything that has risen, which attenuates every kind of diversity in order to bring about a uniform distribution that physicists call the maximum state of entropy and housekeepers, as well as sociologists, call the maximum of disorder.