 Hume had confronted the conflict between these propositions by denying (3) and (4). For Hume, our visual impressions are compounds that consist of a number of minimally visible, coloured points that are disposed alongside another in space, but the notion that impressions and ideas inhere in some mental substance is unintelligible, whether this substance is taken to be material or immaterial. Reid, in contrast, had insisted on (3) and (4) but had declared that the term “colour” is used equivocally in (1) and (2). We experience sensations of colour, which are unextended states of feeling experienced by the mind in just the same way as it experiences feelings of pleasure or pain. But colour terminology is most often used to refer to some unknown thing in external objects that causes us to experience these sensations. These external, so-called “coloured” objects are conceived as being extended and figured, but the mind does not become aware of them by contemplating some internal, iconic representation or image. It has a thought that refers to them. Affection of our sense organs does not produce an impression or image; it occasions a thought. The thought itself is unextended, like the mind whose state it is, but it is a thought of or about an object. The object is thought to possess a quality of extension, as well as to be a cause of a certain concomitant sensation of colour. But the thought that this object is extended and a cause of a sensation of colour is itself neither extended nor coloured. So for Reid, either “colours” are powers in extended, external objects to bring about sensations in us, in which case they are not sensations had by the mind, or they are sensations had by the mind, in which case they are not extended. 