A concept in philosophy of science first described by Whewell, especially in his Philosophy of the Inductive Sciences (1840). Whewell highlighted the process whereby inductions ‘tie together’ facts by the formation of new ideas. Thus separate pieces of evidence may tie together to support a conclusion whose total credibility is then greater than that given by any individual piece of evidence. A good hypothesis not only predicts facts of diverse kinds, but shows that underneath the diversity there is a fundamental unity. Although Whewell is perhaps over-optimistic in thinking that there is one ‘right’ unifying conception to be found in any branch of science, the virtues he points out are extremely important.