a conventional value and which are based on the carelessly constructed concepts of the vulgar, with things themselves.  Here Bacon warns us to keep close to things.  The idola specus are individual prepossessions which interfere with the apprehension of the true state of affairs, such as the excessive tendency of thought toward the resemblances or the differences of things, or the investigator’s habit of transferring ideas current in his own department to subjects of a different kind.  Such individual weaknesses are numberless, yet they may in part be corrected by comparison with the perceptions of others.  The idola tribus, finally, are grounded in the nature of the human species.  To this class belong, among others, illusions of the senses, which may in part be corrected by the use of instruments, with which we arm our organs; further, the tendency to hold fast to opinions acceptable to us in spite of contrary instances; similarly, the tendency to anthropomorphic views, including, as its most important special instance, the mistake of thinking that we perceive purposive relations everywhere and the working of final causes, after the analogy of human action, when in reality efficient causes alone are concerned.  Here Bacon’s injunction runs, not to interpret natural phenomena teleologically, but to explain them from mechanical causes; not to narrow the world down to the limits of the mind, but to extend the mind to the boundaries of the world, so that it shall understand it as it really is.

To these warnings there are added positive rules.  When the investigator, after the removal of prejudices and habitual modes of thought, approaches experience with his senses unperverted and a purified mind, he is to advance from the phenomena given to their conditions.  First of all, the facts must be established by observation and experiment, and systematically arranged,[1] then let him go on to causes and laws.[2] The true or scientific induction[3] thus inculcated is quite different from the credulous induction of common life or the unmethodical induction of Aristotle.  Bacon emphasizes the fact that hitherto the importance of negative instances, which are to be employed as a kind of counter-proof, has been completely overlooked, and that a substitute for complete induction, which is never attainable, may be found, on the one hand, in the collection of as many cases as possible, and, on the other, by considering the more important or decisive cases, the “prerogative instances.”  Then the inductive ascent from experiment to axiom is to be followed by a deductive descent from axioms to new experiments and discoveries.  Bacon rejects the syllogism on the ground that it fits one to overcome his opponent in disputation, but not to gain an active conquest over nature.  In his own application of these principles of method, his procedure was that of a dilettante; the patient, assiduous labor demanded for the successful promotion of the mission of natural investigation was not his