"London is north of Madrid" corresponds to the fact that London is north of Madrid. There are significant differences between the proposition and the fact. The proposition is a set of ideas or concepts, related in a particular way. The fact consists of buildings, people, institutions, and so on, located at various points on the Earth's surface. Because of this we have the following dilemma formulated by Gottlob Frege:

1. The proposition and the fact share all their properties. But then the proposition and the fact would be identical, so it would not make sense to say that one corresponds to the other.
2. The proposition and the fact have different properties. In that case, they can only correspond more or less; there are degrees of correspondence. But then truth cannot consist in correspondence, because there cannot be degrees of truth. A proposition is either true or false. ^[1]

There is an argument to make that we do talk about things being approximately true. Let's call one of these propositions P. If P is approximately true, it means that it must be derived from some proposition P* which is strictly speaking true. But then we are back to the dilemma. ^[1]