© C.O. Evans
 The logical dependence of mental imagery on the possession of sense-organs can also be brought out in another, more obvious, way. Once again we return to the question of attention. Some of
the activities we practise we can practise simultaneously: we can whistle while we walk. Others cannot be carried on at the same time: we cannot whistle while we talk. The same is true of our sense-organ activities. I cannot attentively listen to something and at the same time listen for something else. The one activity impedes the other. Now the point I wish to make in this connection is that attentive sense-organ activities cannot be engaged in simultaneously with the activity of forming corresponding mental images. Take the case of looking at one's mother attentively. If one is doing that one cannot at the same time form a visual image of her. The 'being appeared to' which is the seeing precludes the 'being appeared to' which is the imaging. The two experiences are incompatible in that they seem to compete for the same logical space, and the success of the one precludes the success of the other. It is rather like the case of the impossibility of an expanse being simultaneously red and green all over. This means that in order, say, to form a visual image I must suspend the sense-organ activity of looking (in any of its modes). I do this by ceasing to focus attentively on what I see, and allow what I see to submerge into a ground for the visual image. (That is if I do not take the short-cut of closing my eyes, in which case there is of course no question but that I cease the activity of looking.)
The importance of this state of affairs for my argument is easy to appreciate. In the first place, this is a result one would expect on the sentient approach, but not one that would have an explanation on the phantom approach - according to which there should be no more difficulty about simultaneously scrutinizing an object visually and having a visual image, than there is in simultaneously whistling and walking. In the second place, it shows that attention is involved in the incompatibility between the perceptual activity and the imaging activity. And lastly, and most significant of all, it shows that the imaging activity is dependent upon the suspension of a bodily activity - viz. sense-organ activity. But the suspension of a bodily activity entails muscular inhibition. Thus the analysis substantiates Ribot's claim that a necessary condition of image formation is the inhibition of interfering muscular movement. But it does more than just show that Ribot is right; it also contains an explanation of why he is right, and this explanation was not one that he was aware of, so it takes the theory beyond Ribot's version of it. It does so by making it clear that we are dealing in both types of case with 'doings' and the 'doings' are ones in which of necessity
our bodies come into play. We see, therefore, that even such a non-bodily activity as image formation cannot logically be divorced from bodily activities. The investigation has shown, I believe, that the phantom approach should be rejected in favour of the sentient approach.