The propositional variable signifies the formal concept, and its values signify the objects which fall under this concept.
Every variable is the sign of a formal concept.
For every variable presents a constant form, which all its values possess, and which can be conceived as a formal property of these values. Wherever it is used otherwise, i.e. as a proper concept word, there arise senseless pseudo-propositions. And it is senseless to speak of the number of all objects . We can determine the general term of the formal series by giving its first term and the general form of the operation, which generates the following term out of the preceding proposition. The question about the existence of a formal concept is senseless.