Logical and psychological analysis sharply separated, without minimizing the importance of either. Logic does not rest upon psychology, although it is true to say that in the synthetical (methodeutic) part of logic, certain psychological principles ought to be considered. Logic does appeal, however, to mathematics, phenomenology, and esthetics.
Esthetics and logic, Logic (modal see Modality), Mathematics and logic (and map problem see also Maps fourcolor problem), Meaning, Methodeutic (see also Iogic Normative science), Phenomenology, Psychology
(Meaning Preface to the volume)