The concrete terms man, mortal, and so forth are analogous to the substitution values of the schematic placeholders A, B, C, which were called the "matter" (Greek hyle, Latin materia) of the argument.
Russell wrote: "Some kind of knowledge of logical forms, though with most people it is not explicit, is involved in all understanding of discourse.
It is the business of philosophical logic to extract this knowledge from its concrete integuments, and to render it explicit and pure.
[8] It consists of stripping out all spurious grammatical features from the sentence (such as gender, and passive forms), and replacing all the expressions specific to the subject matter of the argument by schematic variables.
Thus, for example, the expression "all A's are B's" shows the logical form which is common to the sentences "all men are mortals", "all cats are carnivores", "all Greeks are philosophers", and so on.
In semantic parsing, statements in natural languages are converted into logical forms that represent their meanings.