In recent literature in the philosophy of mind and language, one finds a variety of examples that raise serious problems for the traditional analysis of belief as a two-term relation between a believer and a proposition. My main purpose in this essay is to provide a critical test case for any theory of the propositional attitudes, and to demonstrate that this case really does present an unsolved puzzle. Chapter I defines the traditional, propositional analysis of belief, and then introduces a (...) distinction, motivated by the intuitions that underlie Kripke's arguments for direct reference, between purely qualitative and individual propositions. Beliefs typically expressed using proper names, indexicals or demonstratives appear to relate the believer to individual propositions with the entity that may be referred to as subject constituent. Chapter II presents the critical test case . In this and Chapters III-VI it is used to show that the latter sorts of beliefs are not analyzable as dyadically relating the believer to individual propositions. The case constitutes a genuine counterexample to the traditional analysis only if it is possible for a believer to believe an individual proposition with a contingent thing other than herself as a constituent; and the believer in the case is in optimum conditions for believing an individual proposition. In Chapters III, IV, and VI, I criticize views prompted by rejection of , and in Chapter V, I criticize Stalnaker's view, which rejects . Chapter VI also considers the non-traditional, triadic analyses of belief proposed by Kaplan and Richard; they fall prey to the main criticisms of Chapter V. In the Postscript, I give a comparative assessment of approaches to resolving the Two Tubes Puzzle, and I place it in historical context by pointing out the puzzle's similarities to the 'problem of sense data' . Correlatively, I indicate the bearing of Methodological Solipsism on future attempts to solve the puzzle. My conclusion is that although the puzzle remains a puzzle, it gives us reason to supplement, rather than completely abandon, the use of propositions in the analysis of thought; and I say what a supplementing solution must do to remain faithful to the intuitions of Chapter I. (shrink)