 Empirical propositions contain at least one intuition. Most important are those empirical propositions whose subject idea is an intuition. These are propositions about perceptions or sensations, i.e., in Bolzano’s words, about certain changes in our minds, caused by other inner events or by external sensory stimuli. The subject idea of a “private” empirical proposition of this kind is usually expressed by a word such as ‘that’, denoting, e.g., a certain color sensation. No wonder that the indexicals ‘that’ and ‘I’ play such a prominent role in Bolzano’s epistemology (in WL III) although they do not have a place in his logical World 3 (cf. section 3.4). The reason for this seems to be that our empirical knowledge is based on immediate perceptual judgments, i.e., judgments that “grasp” (in the sense of \(\mathbf{G})\) a certain kind of an empirical proposition. The subjective subject idea of such an immediate perceptual judgment is a subjective intuition for whose expression an indexical such as ‘that’ or ‘I’ seems to be indispensable.