2. Lotze has to wrestle with this question of validity in a further aspect: What constitutes the objectivity of thinking as a total attitude, activity, or function? According to his own statement, the meanings or valid ideas are after all only building-stones for logical thought. Validity is thus not a question of them in their independent existences, but of their mutual reference to each other. Thinking is the process of instituting these mutual references; of building up the various scattered and independent building-stones into the coherent system of thought. What is the validity of the various forms of thinking which find expression in the various types of judgment and in the various forms of inference? Categorical, hypothetical, disjunctive judgment; inference by induction, by analogy, by mathematical equation; classification, theory of explanation--all these are processes of reflection by which mutual connection in an individualized whole is given to the fragmentary meanings or ideas with which thought as it sets out is supplied. What shall we say of the validity of such processes? On one point Lotze is quite clear. These various logical acts do not really enter into the constitution of the valid world. The logical forms as such are maintained _only_ in the process of thinking. The world of valid truth does not undergo a series of contortions and evolutions, paralleling in any way the successive steps and missteps, the succession of tentative trials, withdrawals, and retracings, which mark the course of our own thinking.[41] Lotze is explicit upon the point that it is only the thought-content in which the process of thinking issues that has objective validity; the act of thinking is "purely and simply an inner movement of our own minds, made necessary to us by reason of the constitution of our nature and of our place in the world" (Vol. II, p. 279). Here the problem of validity presents itself as the problem of the relation of the act of thinking to its own product. In his solution Lotze uses two metaphors: one derived from building operations, the other from traveling. The construction of a building requires of necessity certain tools and extraneous constructions, stagings, scaffoldings, etc., which are necessary to effect the final construction, but yet which do not enter into the building as such. The activity has an instrumental, though not a constitutive, value as regards its product. Similarly, in order to get a view from the top of a mountain--this view being the objective--the traveler has to go through preliminary movements along devious courses. These again are antecedent prerequisites, but do not constitute a portion of the attained view.