  Bacon came to the fundamental insight that facts cannot be collected from nature, but must be constituted by methodical procedures, which have to be put into practice by scientists in order to ascertain the empirical basis for inductive generalizations. His induction, founded on collection, comparison, and exclusion of factual qualities in things and their interior structure, proved to be a revolutionary achievement within natural philosophy, for which no example in classical antiquity existed. His scala intellectus has two contrary movements “upwards and downwards: from axiomata to experimenta and opera and back again” (Pérez-Ramos 1988, 236). Bacon's induction was construed and conceived as an instrument or method of discovery. Above all, his emphasis on negative instances for the procedure of induction itself can claim a high importance with regard to knowledge acquisition and has been acclaimed as an innovation by scholars of our time. Some have detected in Bacon a forerunner of Karl Popper in respect of the method of falsification. Finally, it cannot be denied that Bacon's methodological program of induction includes aspects of deduction and abstraction on the basis of negation and exclusion. Contemporary scholars have praised his inauguration of the theory of induction. This theory has been held in higher esteem since the 1970s than it was for a long period before (see the work of Rees, Gaukroger and Pérez-Ramos 1988, 201–85). Nevertheless, it is doubtful that Bacon's critics, who were associated with the traditions of positivism and analytical philosophy, acquired sufficient knowledge of his writings to produce solid warrants for their criticisms (Cohen 1970, 124–34; Cohen 1985, 58ff.; on the general problem of induction see, e.g.,  Hempel 1966; Swinburne (ed.) 1974; Lambert and Brittan 1979 [1987]).  In comparison to the neglect of Bacon in the twentieth century, a more recent and deeper assessment of his work has arisen in connection with the “Oxford Francis Bacon” project, which was launched in the late 1990s by Graham Rees, who directed it until his death in 2009; it is now under the general editorship of Brian Vickers.