Philosophy aims at the logical clarification of thoughts. Philosophy is not a body of doctrine but an activity.
Geometry, is not concerned with the relation of the ideas involved in it to objects of experience, but only with the logical connection of these ideas among themselves.
Logic is the most useful tool of all the arts. Without it no science can be fully known.
No, no, you are not thinking, you are just being logical.
All concepts, even those which are closest to experience, are from the point of view of logic freely chosen conventions.
Logic takes care of itself; all we have to do is to look and see how it does it.
The supreme task of the physicist is the discovery of the most general elementary laws from which the world-picture can be deduced logically. But there is no logical way to the discovery of these elemental laws. There is only the way of intuition, which is helped by a feeling for the order lying behind the appearance, and this Einfühlung [literally, empathy or 'feeling one's way in'] is developed by experience.
Reason is a harmonising, controlling force rather than a creative one. Even in the most purely logical realms, it is insight that first arrives at what is new.
The logic of the world is prior to all truth and falsehood.
Logic is the technique by which we add conviction to truth.
Logic will get you from A to B. Imagination will take you everywhere.
