The thinker, like the carpenter, is at once stimulated and checked in every stage of his procedure by the particular situation which confronts him. A person is at the stage of wanting a new house: well, then, his materials are available resources, the price of labor, the cost of building, the state and needs of his family, profession, etc.; his tools are paper and pencil and compass, or possibly the bank as a credit instrumentality, etc. Again, the work is beginning. The foundations are laid. This in turn determines its own specific materials and tools. Again, the building is almost ready for occupancy. The concrete process is that of taking away the scaffolding, clearing up the grounds, furnishing and decorating rooms, etc. This specific operation again determines its own fit or relevant materials and tools. It defines the time and mode and manner of beginning and ceasing to use them. Logical theory will get along as well as does the practice of knowing when it sticks close by and observes the directions and checks inherent in each successive phase of the evolution of the cycle of experience. The problem in general of validity of the thinking process as distinct from the validity of this or that process arises only when thinking is isolated from its historic position and its material context (see _ante_, p. 95). 3. But Lotze is not yet done with the problem of validity, even from his own standpoint. The ground shifts again under his feet. It is no longer a question of the validity of the idea or meaning with which thought is supposed to set out; it is no longer a question of the validity of the process of thinking in reference to its own product; it is the question of the validity of the product. Supposing, after all, that the final meaning, or logical idea, is thoroughly coherent and organized; supposing it is an object for all consciousness as such. Once more arises the question: What is the validity of even the most coherent and complete idea?--a question which arises and will not down. We may reconstruct the notion of the chimera until it ceases to be an independent idea and becomes a part of the system of Greek mythology. Has it gained in validity in ceasing to be an independent myth, in becoming an element in systematized myth? Myth it was and myth it remains. Mythology does not get validity by growing bigger. How do we know the same is not the case with the ideas which are the product of our most deliberate and extended scientific inquiry? The reference again to the content as the self-identical object of all consciousness proves nothing; the subject-matter of a hallucination does not gain validity in proportion to its social contagiousness.