A Defense of Hume on Identity Through Time

323 A DEFENSE OF HUME ON IDENTITY THROUGH TIME A durable complaint against Hume is that he blatantly begs the question in his Treatise account of our acquisition of the idea of identity through time. Green and Grose made the accusation in 1878; one hundred years later Stroud echoed the same accusation, its force and liveliness seemingly undiminished. I suggest that this accusation is based on a tempting but unwarranted assumption about Humean perceptions. It is unwarranted despite Price's arguments for it. When the assumption is corrected Hume is exonerated. This defense prepares the way for a new understanding of Hume's subtle and important theory of identity. Clarifying his theory is the goal; defending him is the means. I will merely summarize the Green and Grose interpretation, saving detailed examination for Stroud's. Stroud's version seems more tightly argued for and spares one the problems of interpreting commentators from a different philosophical tradition. Green and Grose run together Hume's account of the acquisition of the idea of identity, with his account of the application of that idea to a succession of related perceptions. This fully intended confusion can be explained by their understanding of Hume's claim that "impressions are ... perishing existences." (T 194) They assume that for Hume no perception (impression or idea) is a unity if it exists at an interval of time composed of a succession of times. Rather the perception is really a succession of perceptions. Their assumed interpretation makes Hume seem to them to beg the question as follows: To acquire the idea of identity through time is to acquire the idea of something 324 which is unitary and exists at a succession of times. But any impression which might give this idea is really a succession of related impressions. A succession of related impressions can convey the idea of identity only by being confused with a unitary impression which exists at a succession of times. Such confusion would be possible only for someone who already had the idea of something unitary which exists at a succession of times. So the idea of 2 identity can be acquired only if it is already had. In other words, Hume claims that an impression had for a relatively long time gives the idea of identity. Any long impression is really a succession. A succession can give the idea of identity only if it is confused with something that has identity. That confusion requires the idea of identity already. So Hume begs the question. There are gaps in this argument. But its influence has been important and its structure is clear: If we assume that perceptions are exceedingly brief, then Hume begs the question. (I will call the assumption 'the prosecution's assumption.') Stroud's argument that Hume begs the question has the same structure, or so I will argue. The role of the prosecution's assumption is not immediately apparent, but it is a crucial role. Stroud's accusation is as follows: By Hume's definition, identity is the invariableness and uninterruptedness of an object through a supposed change in time. (T 201) However, on Hume's account of acquiring the concept of identity, the acquisition involves imagining a change in time without any variation or interruption in an object. But that just ¿s, by definition, to imagine the object's identity through the change in time. So acquiring the concept of identity requires an act of imagination involving the 325 concept of identity. So, Stroud concludes, on Hume's account the concept of identity can be acquired only 3 if it is had. Hume's account begs the question. I think it is usually unwise to attribute blunders to subtle thinkers. I will not do it to Hume, nor to his commentators. I will argue that what Hume presupposes in explaining identity through time is a little different from identity through time. Thus the presupposition is not question-begging. More specifically , I will argue that Hume distinguishes three technical concepts, three ways to take up time: (i) merely occupying an interval of time, (ii) having duration for an interval of time, and (iii) being identical through an interval of time. Concept (iii...