The primary properties?

Science is concerned not just with objects but also with their various aspects, such as their colors, temperatures, sizes, and shapes. These aspects, or properties, are generally thought to be of at least two kinds: primary properties, such as shape, size, and motion and secondary ones, such as temperature and color. However, there is little agreement on just what the difference is between these two kinds of properties. An argument has recently been put forth that assumes the two kinds of properties differ only in that the secondary ones are dependent on the conditions under which they are observed. This paper suggests, however, that since the primary properties depend on conditions, too, any argument based on this assumption is flawed. There are two main traditional accounts of the distinction. The first account of the distinction-the ideas of primary qualities resemble the properties that cause these ideas, whereas those of the secondary ones do not resemble them-relies on what to many is an implausible assumption, that some of our ideas resemble features of the world and we can speak intelligibly about such resemblances. This paper suggests that we cannot, and hence we have no more reason to believe that the ideas of the primary qualities resemble aspects of the world than we do that those of the secondary qualities do so. The second traditional account-primary properties are those a body has, however small it might be, whereas secondary properties are a consequence just of relations between bodies-fares better than the other two accounts. However, the notion of force posed a serious problem for this second basis for the distinction, one that has, astonishingly, hardly found its way into the philosophical literature.