 For Frege the opposition between truth and what-is-taking-to-be-true is closely linked to the distinction between accepting and rejecting the realm of objective and non-real entities. Frege insists that the realm of the non-real is not identical with the realm of the psychological and subjective. His example of objective, non-psychological entities are numbers. Numbers are not ideas since they are the same for all subjects (1893, XVIII). Moreover, Frege tries to convince us that the denial of the objectivity and non-reality of numbers and concepts leads fairly directly into idealism and solipsism. Since psychological logicians try so hard to break down the distinction between the realms of the objective-ideal and the subjective-psychological, they easily are tempted to go further and challenge the borderline between the subjective-psychological and the objective-real. The resulting standpoint is idealism and solipsism: idealism since the only existing entities are ideas; solipsism since all ideas are relative to subjects. And thus the possibility of communication is a further victim of their efforts (1893, XIX). Again Frege is eager to show that Erdmann’s logic is guilty of the charges. He therefore points out that Erdmann calls both hallucinated objects and numbers ‘objects of an ideal nature’; that Erdmann fails to distinguish between acts and contents of judgments; and that Erdmann lacks the conceptual resources to distinguish between ideas and realities (1893, XX–XXIII). 