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Hume on the Idea of Existence1 Phillip D. Cummins One, the primary, aim of this paper is to understand an argument Hume employed to defend his contention that there is no special or distinctidea ofexistence. This contention he expressedvariouslyin the following passage: The idea ofexistence, then, is the very same with the idea of what we conceive tobe existent. To reflect on any thing simply, and to reflect on it as existent, are nothing different from each other. That idea, when conjoin'd with the idea of any object, makes no addition to it. Whatever we conceive, we conceive to be existent. Any idea we please to form is the idea ofa being; and the idea of a being is any idea we please to form.2 My secondary aim is to understand what the quoted claim amounts to as a characterization of the idea of existence. I am among those who have serious difficulty understanding what precisely Hume is here claiming. Specifically, I am not sure how, if at all, his position on the idea ofexistence fits with other elements ofhis theory ofthought.3 For example, earlier in the Treatise, in "OfAbstract Ideas," Hume argued that under suitable conditions of habituation and linguistic competence, a single simple4 idea could be the idea ofboth a particular object, a line drawn on a particular sheet ofpaper, and a type ofobject, line in general (T 20-24). Further, on the basis of appropriate comparisons, a single simple idea can also be the idea oftwo different quaUties, purple and extended, for example (T 24-25, 34). The former claim is the positive component ofHume's account ofabstract thinking; the latter is the positive component of his position on distinctions of reason. Hume goes out ofhis way to distinguish his position on the idea of existence from his position on distinctions of reason (T 67). As for how it differs, ifat all, from his position on abstract ideas, a matter by no means obvious, Hume says nothing at all. His silence does not preclude speculation on the subject—on the contrary, it makes such speculation unavoidable—but it does give special importance to his brief and puzzhng proof that there is no special or distinct idea of existence. Volume XVII Number 1 61 PHILLIP D. CUMMINS I. Hume's Argument In making his case that we have no distinct idea of existence Hume first insists that we have an idea of existence, appealing to what he regards as an undeniable matter of psychological fact. He writes, There is no impression nor idea ofany kind, ofwhich we have anyconsciousness or memory, thatis not conceiVd as existent; and 'tis evident, that from this consciousness the most perfect idea and assurance ofbeing is deriv'd. (T 66) The argument seems to comprise the following propositions: attending to consciousness and memory reveals that all the perceptions we experience or remember are believed to exist; one cannot beUeve in the existence of something unless one has an idea of existence; therefore, there is an idea ofexistence (being) which in some way is derived from consciousness and memory. Hume next formulates what he calls a dilemma. From hence we may form a dilemma, the most clear and conclusive that can be imagin'd, viz. that since we never remember any idea or impression without attributing existence toit, the idea ofexistence must eitherbe deriv'd from a distinct impression, conjoin'd with every perception or object ofour thought, or must be the very same with the idea of the perception or object. (T 66) The alternatives seem clear: either, in believing in the past existence of, say, a blue spot once seen, one has two ideas, one of the blue spot and a different one of existence, or one has only one idea, which somehow is both the idea of the spot and the idea ofexistence. What is not immediately obvious is why Hume speaks ofa dilemma. From the supposed psychological fact (we never remember any idea or impression without attributing existence to it) and its corollary (we have an idea ofexistence) Hume develops a disjunction (either the idea ofexistence is derived from a distinct impression conjoined with every perception, or...