Sensa have properties, such as shape, size, hardness, colour, loudness and coldness. The existence of such sensa, and their presence to one's mind in sensation, lead one to judge that a physical object exists and is present to one's senses. Sensa have been supposed by many philosophers to be in some way mental. Science also ignores it, because, although in theory it makes an equivalent distinction, it uses it simply as an excuse for ignoring sensa and concentrating on physical objects and processes. The English talk of a sensation of smell, whereas the Scots more usually speak of 'feeling' a smell. The scientific view needs to be completely restated in terms of the sensum theory. And this is not easy, because the scientific theory assumed that we really were sensing the contour of the actual physical object out in space, and that our sensations were due to what was going on within that contour.