[25] It is interesting to see how explicitly Lotze is compelled finally to differentiate two aspects in the antecedents of thoughts, one of which is necessary in order that there may be anything to call out thought (a lack, or problem); the other in order that when thought is evoked it may find data at hand--that is, material in shape to receive and respond to its exercise. "The manifold matter of ideas is brought before us, not only in the _systematic order of its qualitative relationships_, but in the rich _variety of local and temporal combinations_.... The _combinations of heterogeneous ideas_ ... form the _problems_, in connection with which the efforts of thought to reduce coexistence to coherence will _subsequently_ be made. The _homogeneous or similar_ ideas, on the other hand, give occasion to separate, to connect, and to count their repetitions" (I, 33, 34; italics mine). Without the heterogeneous variety of the local and temporal juxtapositions there would be nothing to excite thought. Without the systematic arrangement of quality there would be nothing to meet thought and reward it for its efforts. The homogeneity of qualitative relationships, _in the pre-thought material_, gives the tools or instruments by which thought is enabled successfully to tackle the heterogeneity of collocations and conjunctions also found in the same material! One would suppose that when Lotze reached this point he might have been led to suspect that in his remarkable adjustment of thought-stimuli, thought-material, and thought-tools to one another, he must after all be dealing, not with something prior to the thought-function, but with the necessary structures and tools of the thought-situation. [26] _Supra_, p. 113. [27] For the identity of sensory experience with the point of greatest strain and stress in conflicting or tensional experience, see "The Reflex Arc Concept in Psychology," _Psychological Review_, III, 57. [28] For the "accessory" character of thought, see Lotze, I, 7, 25-27, 61, etc.