A major, overarching cluster of problems central to the philosophy of science and certainly underlying much of the debate in the recent literature is how scientific theories are constructed, how they are judged or selected, and what type of knowledge they give us. There are two aspects of answers to any of these three questions: what has actually occurred according to the historical record and what is the rational status of each of these activities or of the knowledge produced. A simple schema, that is based on induction and the hypothetical-deductive method and that provides answers to the above queries, is the sequence: observation, hypothesis, prediction, confirmation. This model or picture of science has a long tradition. We can see its roots already in Bacon's (1620 (1960, pp. 43–4 and 98-100)) advocating a slow and careful ascent from particulars to generalities (Aphorisms, Bk. I, XIV, XXII, CIII–CVII). He urged use of a combination of induction and deduction in arriving at knowledge. In Bacon's ladder of axiom, one is to make modest generalizations based on specific observations and data, check these modest theories by comparing their predictions with facts once again, then combine these generalizations into more general ones, check their predictions against observations, and in this way carefully proceed to the most general axioms, theories or laws. Whewell (1857, Vol. I, p. 146) speaks of the epochs of induction, development, verification, application and extension.