Notes on Hume's Treatise
by G. J. Mattey
Book I, Part II OF THE IDEAS OF SPACE AND TIME
§. III. Of the other qualities of our ideas of space and time.
Impressions similar to the idea of extension must be produced, either from sight or internal impressions. The latter cannot do the job.
In the impression of an object (the table before me) we have "the impressions of colour'd points, dispos'd in a certain manner," and nothing more.
[We can make a distinction of reason] and "omit the peculiarities of colour" and form an abstract idea, applying to points of different colors and even to solid points.
The idea of time is derived from succession of all kinds of impressions.
There must be a perceivable succession in order for time to make its appearance before the mind. [Space is equated with extension, in that Hume contrasts the abstract idea of space with that of time. But he had just introduced the abstract idea of extension.]
If there is no successive perception, there no notion of time. Time has parts which are not coexistent, but "an unchangeable object" producing only co-existent impressions, produces none of succession.
There is no impression of time, only an idea arising from the manner in which impressions appear to it. It may consider the manner in which perceptions make their appearance, and "may afterwards consider without considering these particular sounds, but may conjoin it with any other objects."
The idea of duration does not apply to unchangeable objects. It is by a fiction that we apply the idea of time (see § V).
Indivisibility of the parts of complex ideas. A simple idea cannot be one of extension. Our idea of a simple and indivisible point is that of "their colour or tangibility."