A critical analysis of the thesis of the symmetry between explanation and prediction : including a case study of evolutionary theory

One very significant characteristic of Hempel's covering-law models of scientific explanation, that is, the deductive-nomological model and the inductive-statistical model, is the supposed symmetry between explanation and prediction. In brief, the symmetry thesis asserts that explanation and prediction have the same logical structure; in other words, if an explanation of an. event had been taken account of in time, then it could have served as a basis for predicting the event in question, and vice versa. The present thesis is a critical analysis of the validity of this purported symmetry between explanation and prediction. The substance of the thesis begins with a defence against some common misconceptions of the symmetry thesis, for example, the idea that the symmetry concerns statements but not arguments. Specifically, Grunbaum's interpretation of the symmetry thesis as pertaining to the logical inferability rather than the epistemological symmetry between explanation and prediction is examined. The first sub-thesis of the symmetry thesis, namely that "Every adequate explanation is a potential prediction," is then analyzed. Purported counterexamples such as evolutionary theory and the paresis case are critically examined and consequently dismissed. Since there are conflicting views regarding the nature of explanation and prediction in evolutionary theory, a case study of the theory is also presented. Next, the second sub-thesis of the symmetry thesis, namely that "Every adequate prediction is a potential explanation," is discussed. In particular, the barometer case is discharged as a counterexample to the second sub-thesis when the explanatory power of indicator laws is properly understood. Finally, Salmon's current causal-relevance model of explanation, which claims to be an alternative to Hempel's inductive-statistical model, is critically analyzed. A modified inductive-statistical model of explanation is also proposed. This modified model retains the nomological ingredient of Hempel's original inductive-statistical model, but it is immune to criticisms raised against the latter. In conclusion, I maintain that there is indeed a symmetry between explanation and prediction. But since deductive-nomological explanation and prediction are essentially different from inductive-statistical explanation and prediction, the form the symmetry takes between deductive-nomological explanation and prediction differs from the form it exhibits between inductive-statistical explanation and prediction.Arts, Faculty ofPhilosophy, Department ofGraduat