The Import of Hume's Theory of Time

119. THE IMPORT OF HUME'S THEORY OF TIME In this paper I examine the significance of Hume's theory of time for some of the more famous of the doctrines in the Treatise, and how it works as a basis for his peculiar brand of scepticism, a basis that is at least as important in this regard as his principle that all ideas are derived from some original impression. To bring into relief some of the peculiarities of Hume's theory of time we may observe that it was not uncommon in the seventeenth and eighteenth centuries to distinguish between space and extension and between time and duration, to say, as does for example Leibniz, that "in some way extension is to space as duration is to time", and perhaps also to agree with him "that duration and extension are attributes of things, but time and space are taken to be something outside of things and serve to measure them. " Duration taken as an attribute of things or substantives connotes the permanence, or perseverance, or continuation of the existence of such substantives. Thus Descartes says, "the duration of each thing is a mode [he subsequently calls it an 'attribute'] under which we consider the thing in so far as it continues to exist" (French version) or "perseveres 2 in existence" (Latin version) . Or Spinoza: "Duration is the attribute under which we conceive the existence of created things in so far as they persevere in their own 3 actuality". But though duration refers to things as persevering or continuing in existence, it applies equally, as Descartes indicates, to both changing and unchanging things. In order to comprehend the duration of all things under the same measure we usually compare their duration with the duration of the greatest and most regular motions, which are those which create years and days, and these we call time.4 Spinoza's account of duration and time are much the same. Duration is the primary notion and time presupposes it. Going beyond Hume to Kant we find that in distinguishing 120. three modes of time, namely duration, succession and coexistence , Kant argues that succession presupposes duration and that all time determinations of change (or succession) presuppose substance as that which is permanent or continuant through change. In Hume, however, we find no distinction between space and extension, nor between time and duration. These are merely two pairs of synonyms. In the case of space Hume seems to prefer on the whole to talk about extension, probably because extension lends itself more easily to discussion of divisibility. In the case of time, however, which he, defines as succession, he is indeed aware of the view which we have just been considering, according to which duration is referred primarily to an object qua con- . tinuing or persevering or enduring, whether or not undergoing successive changes. This concept of duration, he says, I take to be the common opinion of philosophers as well as of the vulgar. (T37) Duration in this common philosophical and vulgar sense is not a synonym of Humean time or succession, and it is for Hume, a "fiction", something falsely attributed to objects. Why is this so? 'Tis evident, that time or duration [Hume is here taking the two terms as synonyms] consists of different parts... 'Tis also evident, that these parts are not co-existent: For that quality of the co-existence of parts belongs to extension, and is what distinguishes it from duration. Now as time is compos 'd of parts, that are not co-existent; an unchangeable object, since it produces none but co-existent impressions , produces none that can give us the idea of time; and consequently that idea must be deriv'd from a succession of changeable objects, and time in its first appearance can never be sever 'd from such a succession (T35,36) Although Hume maintains that there is no idea which is not derived from some original impression, it would appear that this is not strictly so with the idea of time [or, for that matter with the idea of space] . Rather time is the manner or way in which impressions appear to the mind, namely...