There have been two main streams contributing to the development of the field of ``qualitative reasoning''. The first of these, usually referred to as qualitative physics, builds on the work of de Kleer, who pioneered the use of qualitative methods in solving engineering problems. The second is a program initiated by Hayes, with the aim of developing a ``Naive Physics'', which Hayes defines as ``a large-scale formalism'' of commonsense knowledge.
Nearly all published work in qualitative reasoning acknowledges both de Kleer and Hayes, but the majority follows the example of de Kleer's work, in that it attempts to analyse specific physical situations in qualitative terms. In contrast to this approach, Hayes recommends that naive physics should consider a wide range of human experience in developing qualitative models. The following two sections present firstly a historical overview of developments in qualitative physics, and secondly a brief discussion of the aims of naive physics, which considers how far qualitative reasoning research has progressed toward those aims.