In general, in his opening paragraphs, Erdmann defines Logic as the "science of the formal presuppositions of valid judgments concerning the objects of inner and outer perception" (p. 15). As formal, the presuppositions which logic studies, i.e. the presuppositions of "valid," or of "scientific" thinking, are to be distinguished from those material presuppositions which are the topic, on the one hand of metaphysics, on the other hand of special science. Logic is then (p. 16) a general or formal "normative" science of the thinking process. Its office is thus indeed different from that of the psychology of the thinking process (p. 18); but it is impossible to study norms without understanding actual processes, and if logic (p. 19) is to avoid barren schematism, the logician must base his study upon a psychological analysis of the natural history of the thinking process. To such a natural history Erdmann devotes, in fact, considerable space. The first book of his treatise (pp. 35-186), on the "Gegenstände des Denkens" contains much psychological material. By "objects of thought," Erdmann means the sum total of the "Vorgestelltes" i.e. of that of which we have ideas (p. 81). In his own metaphysic disposed to realism, Erdmann endeavors as far as possible to separate logical and metaphysical problems (pp. 10-12, 77, 81-85). The "Gegenstände der Vorstellungen" or "des Denkens" are therefore not, in general, for the logician, the things in themselves, or "das Transcendente" (p. 10), but the "objects whose elements are given to us in inner or outer perception" (p. 12). These objects it is that in science we are directly thinking about. "Das Transcendente" we conceive only indirectly through the objects of inner or outer experience, and it is in regard to the latter that there arises the general question of Logic (p. 12), viz.: "What is our right to assume the possibility of valid judgment concerning 'das Vorgestellte'?" "Das Vorgestellte" itself consists either of "original objects" or of "derived objects" (p. 38, "ursprüngliche und abgeleitete Gegenstände"). The former correspond to Locke's "ideas" of outer and inner sense. The latter include the ideas of memory, and die abstrakten Vorstellungen. As for Erdmann's use of Vorstellung, as he explains it on p. 36, the word relates to "all contents of consciousness in which objects are presented," and "unconscious Vorstellungen" are self-contradictions. On the other hand, however, the process of Apperception (the word being used in the Herbartian sense) involves mental processes which themselves remain in large part unconscious (p. 42), and Erdmann makes considerable use of the category of the unconscious in mental life, his view of this matter coloring important logical analyses in the course of the book (cf. p. 77, and the argument on p. 210 with regard to Kant's doctrine of the "synthetic" judgments of perception). On the basis of this general theory of Apperception, Erdmann introduces, on p. 45,
