243. If we look to the detailed account which Hume gives of the relation between extension and colour, we find that he avoids the appearance of making one feeling a quality of another, by in fact substituting for colour a superficies of coloured points, in which it is very easy to find extension as a quality because it already is extension as an object. To speak of extension, though a feeling, as made up of parts is just as legitimate or illegitimate as to speak of the feeling of colour being made up of coloured points. The legitimacy of this once admitted, there remains, indeed, a logical question as to how it is that a quality should be spoken of in terms that seem proper to a substance--as is done when it is said to consist of parts--and yet, again, should be pronounced a relation of these parts; but to one who professed to merge all logical distinctions in the indifference of simple feeling, such a question could have no recognised meaning. It is, then, upon the question whether, according to Hume’s doctrine of perception, the perception of an object made up of coloured points may be used interchangeably with the perception of colour, that the consistency of his doctrine of extension must finally be tried. 244. The detailed account is to the following effect:--‘Upon opening my eyes and turning them to the surrounding objects, I perceive many visible bodies; and upon shutting them again and considering the distance betwixt these bodies, I acquire the idea of extension.’ From what impression, Hume proceeds to ask, is this idea derived? ‘Internal impressions’ being excluded, ‘there remain nothing but the senses which can convey to us this original impression.’ ... ‘The table before me is alone sufficient by its view to give me the idea of extension. This idea, then, is borrowed from and represents some impression which this moment appears to the senses. But my senses convey to me only the impressions of coloured points, disposed in a certain manner. ... We may conclude that the idea of extension is nothing but a copy of these coloured points and of the manner of their appearance.’ [1] [1] Pp. 340 and 341. [Book I, part II., sec. III.] Can a ‘disposition of coloured points’ be an impression?