Abstract

In his Particles and Waves, Peter Achinstein gives a precise probabilistic version of theoretical coherence inspired by William Whewell's somewhat vague notion of coherence. Whewell believed that as theoretical science proceeds, it becomes more coherent and rejects false incoherent theories. Achinstein offers a challenge: try to make Whewell's idea more precise while maintaining the properties that Whewell claimed coherence to have. This chapter argues (1) that Achinstein's probabilistic rendition of coherence fails to capture Whewell's notion since the probabilistic rendition of coherence is not an a priori sign of truth and (2) that Achinstein's approach is better seen as a critique of Whewell's central methodological claims than as an interpretation of Whewell's ideas.