SIXTEENTH-CENTURY PHILOSOPHY his guard against the factors that can introduce bias into his observations Bacon lists four of these, and calls them ‘idols’ because they are fetishes which can divert us from the pursuit of truth: there are the idols of the tribe, the idols of the den, the idols of the marketplace, and the idols of the theatre The idols of the tribe are temptations endemic in the whole human race, such as the tendency to judge things by superWcial appearances, the tendency to go along with popular belief, and the tendency to interpret nature anthropomorphically The idols of the den, or cave, are features of individual temperaments which hamper objectivity: some people, for instance, are too conservative, others too ready to seize on novelties Each person has ‘a certain individual cavern of his own, which breaks and distorts the light of nature’ The idols of the marketplace (or perhaps ‘idols of the courts’—idola fori) are snares lurking in the language we use, which contains meaningless, ambiguous, and ill-deWned words Finally the idols of the theatre are false systems of philosophy which are no more than stage plays, whether ‘sophistical’, like Aristotle’s, or ‘empirical’, like contemporary alchemists, or ‘superstitious’ like the Neoplatonists who confuse philosophy with theology The positive task of the researcher is induction, the discovery of scientiWc laws by the systematic examination of particular cases If this is not to be rash generalization from inadequate sampling of nature, we need a carefully schematized procedure, showing us how to mount gradually from particular instances to axioms of gradually increasing generality Bacon oVers a series of detailed rules to guide this process: Suppose that we have some phenomenon X and we wish to discover its true form or explanation We must Wrst make a table of presences—that is to say, we list the items A, B, C, D which are present when X is present Then we make a table of absences, listing items E, F, G, H which are present when X is absent Thirdly, we make a table of degrees, recording that J, K, L, M are present to a greater degree when X is present to a greater degree, and present to a lesser degree when X is present to a lesser degree This is only the preparatory step in the method The real work of induction comes when we start the process of eliminating candidates for being the form of X To be successful a candidate must be present in every case occurring in the table of presences, and absent in every case occurring in the table of absences Bacon illustrates his method with the example of 31