The Origin, Form, and Logic of Qualitative Physical Laws

Recentl~ there has been a areat deal of interest aithin the .\rtificial intelligence communits in des eloping a qualiiause ph~sies (e.g.. qualitatis e process theor~. ens isioning. naive ph~sics) that predicts and explains the behasior of mechanisms in qualitatise terms. The goals for the qualitatise physics are (1) to be far simpler than classical ph~sicsand ~et retain all the important distinctions (e.g.. state, oscillation, gain, momentum) without insokng the mathematics of continuousl~sarsing quantities and differential equations, (2) to produce causal accounts of phssicai mechanisms that are easy to understand, and (3) to proside the foundations for common-sense models for the next generation of expert systems. This paper consists of three parts. First, se present a framework for understanding and unifying the various approaches to qualitative physics as well as posing certain criteria that such a physics should satisfy. Second, we compare and contrast three approaches to qualitative physics. Finally, we explore the use of proofas explanation and the role reduciio ad absurduni plays in qualitative arguments in physics.