A proposition describes of a matter of fact.

A proposition must restrict reality to two alternatives: yes or no. In order to do that, it must describe reality completely. A proposition describes of a matter of fact. Just as a description of an object describes it by giving its external properties, so a proposition describes reality by its internal properties. A proposition constructs a world with the help of a logical scaffolding, so that one can actually see from the proposition how everything stands logically if it is true. One can draw conclusions from a false proposition.

To understand a proposition means to know what is the case if it is true. (One can understand it, therefore, without knowing whether it is true.) It is understood by anyone who understands its constituents. When translating, we do not translate each sentence of one language into a sentence of the other, but merely translate the constituents. (And the dictionary translates not only substantives, but all the parts of speech and it treats them all in the same way.) The meanings of simple signs (words) must be explained to us if we are to understand them. With sentences, however, we make ourselves understood. It belongs to the nature of a sentence that it should be able to communicate a sense new to us.