Logic is simply the language of convenient rationalization in a pseudo-science-loving civilization.

Logic is the necessary product of intelligence and sincerity. It cannot be learned. It is the child of a clear head and a good heart.

Logic is the foundation of the certainty of all the knowledge we acquire.

The system of logic is the realm of shadows, the world of simple essentialities, freed of all sensuous concretion. To study this science, to dwell and to labor in this realm of shadows, is the absolute culture and discipline of consciousness.

The true function of logic ... as applied to matters of experience ... is analytic rather than constructive; taken a priori, it shows the possibility of hitherto unsuspected alternatives more often than the impossibility of alternatives which seemed prima facie possible. Thus, while it liberates imagination as to what the world may be, it refuses to legislate as to what the world is

Mathematics is a method of logic.

Logic is relative.

6.1 The propositions of logic are tautologies.
6.2 Mathematics is a logical method. The propositions of mathematics are equations, and therefore pseudo-propositions.
6.3 The exploration of logic means the exploration of everything that is subject to law. And outside logic everything is accidental.
6.4 All propositions are of equal value.
6.5 When the answer cannot be put into words, neither can the question be put into words. The riddle does not exist. If a question can be framed at all, it is also possible to answer it.

Formal logic, or logistics, is simply the axiomatics of states of equilibrium of thought, and the positive science corresponding to this axiomatics is none other than the psychology of thought.

The sole object of Logic is the guidance of one's own thoughts: the communication of those thoughts to others falls under the consideration of Rhetoric, in the large sense in which that art was conceived by the ancients; or of the still more extensive art of Education.

Logic is not a theory but a reflexion of the world.

The logic of the world which the propositions of logic show in tautologies, mathematics shows in equations.

Logical research means the investigation of all regularity. And outside logic all is accident.

Formal logic is nothing but the study of the properties common to all classifications; it teaches us that two soldiers who are members of the same regiment belong by this very fact to the same brigade, and consequently to the same division; and the whole theory of the syllogism is reduced to this.