  Still more recently, Pelczar has argued (2010a, 2010b) that the Extensional model rests on an inadequate conception of the temporal microstructure of consciousness. An Extensional specious present is a chunk of experiencing which extends over a second or so of ordinary time, so it will inevitably possesses temporal parts – the still briefer chunks of experiencing of which it is composed – and the briefest of these parts will be strictly momentary episodes of experiencing. Since on the Extensional model it takes an interval of time to experience change or succession, these momentary stream-phases will not contain any experience of change: their contents will be entirely static in character. This is problematic, argues Pelczar, because we have good reason to believe it is impossible for such experiences to exist. The grounds for this are phenomenological: ‘When I have an experience as of some smooth continuous change – when watching a leaf drift to the ground, for example, or listening to a steadily rising tone – my experience does not contain or decompose into a series of experiences that are not as of change’ (forthcoming A). Since the briefest of experiences that we can conceive or imagine contains some element of change, or passage – or so Pelczar maintains – we should accept that experience is essentially dynamic, or better: subjectively dynamic. Since the momentary episodes of experience which feature in the Extensional model do not feature change, it seems that Extensional specious presents are composed of ingredients which cannot possibly exist. Retentionalist accounts do not face this difficulty. A Retentionalist specious present is momentary episode of experiencing whose contents are (by hypothesis) subjectively dynamic.