The Origin, Form, and Logic of Qualitative Physical Laws

Abstract

R~c~ntly there has been a great deal of interest within the .\rtificial lntdligcnce community in dc1cloping a qualitati1e physics (e.g .. qualitatil c process theory. em isioning. naive ph) sics) that predicts and explains the beha1 ior of mechanisms in qualitative terms . The goals for the qualitati1e physics are (1} to be far simpler than classical physics and yet retain all the important distinctions (e.g .. state, oscillation. gain. momentum) without invoking the mathematics of continuously var.ing quantities and differential equations. (2} to produce causal accounts of physical mechanisms that are easy to understand, and (3} to provide the foundations for common-sense models for the next generation of expert systems. This paper consists of three parts. First. we present a framework for understanding and unifying the various approaches :o qualitative physics as well >~S 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 proof as explanation and the role reducrio ad absurdum plays in qualitative arguments in physics.