A consequence of the new "mathematicized" metaphysics of Descartes was that a certain gap opened up between the quantitative description of the world put forward by the scientists and the common sense world revealed by the five senses - the world of colors, smells, tastes, sounds, and textures.
Descartes had point out that nothing reaches the brain from the outside world except various "local motions" transmitted through the sense organs. He concluded that the properties in external objects to which we apply the terms "light", "color", smell", "taste", "sound", "heat", and cold" are, so far as we can see, simply various dispositions in the shapes, sizes, positions, and movements of their parts that make them able to set up various kinds of motions in our nerves, which then produce all the various sensations in our soul.
Taking up this theme, the English philosopher John Lock made a radical distinction between primary and secondary qualities of things. Primary qualities such as shape, he argues are utterly inseparable from the body or the object being observed in whatsoever state it is. Descartes took being extended in three dimensions as the essential characteristic of matter.
Locke's list of the basic or primary qualities of matter comprises "solidity, extension, figure (shape) and mobility."
Now as far as our ordinary idea of the objects around us is concerned, we normally conceive of them as having many other qualities in addition to those on Locke's list. For instance, the marigold has a striking color, the pineapple a characteristic taste, the perfume a distinctive aroma, and so on. But these qualities for Locke are merely powers that objects have in order to produce various sensations in us by means of their primary qualities.
Essentially when we conceive of an object as having shape, for example, there is, according to Locke, a "resemblance" between our idea of the object and how it really is: [the] patterns do really exist in the Bodies or the Objects themselves. But when we call an object sweet or blue, there is nothing like our ideas existing in the bodies or Objects themselves. (These are secondary qualities whereas the other qualities are primary).
The real physical nature of the object, therefore, turns out to be for Locke very different in nature from how we often naively suppose it to be. A kind of veil interposes itself between our human sensory awareness of the world on the one hand, and on the other, the world as it "really " is.
