Note 194 — Chapter XX

Inductio quæ procedit per enumerationem simplicem, res puerilis est, et precario concludit, et periculo exponitur ab instantia contradictoria, et plerumque secundum pauciora quam par est, et ex his tantummodo quæ præsto sunt, pronuntiat. At inductio quæ ad inventionem et demonstrationem scientiarum et artium erit utilis, naturam separare debet, per rejectiones et exclusiones debitas; ac deinde post negativas tot quot sufficiunt, super affirmativas concludere; quod adhuc factum non est, nec tentatum certe, nisi tantummodo a Platone, qui ad excutiendas definitiones et ideas, hac certe forma inductionis aliquatenus utitur. Nov. Org. i. 105. In this passage Bacon seems to imply that the enumeration of particulars in any induction is or may be imperfect. This is certainly the case in the plurality of physical inductions; but it doss not appear that the logical writers looked upon this as the primary and legitimate sense. Induction was distinguished into the complete and incomplete. “The word,” says a very moderate writer, “is perhaps unhappy, as indeed it is taken in several vague senses; but to abolish it is impossible. It is the Latin translation of επαγωγη, which word is used by Aristotle as a counterpart to συλλογισμος. He seems to consider it in a perfect, or dialectic, and in an imperfect or rhetorical sense. Thus, if a genus (G.) contained four species (A. B. C. D.), syllogism would argue, that what is true of G. is true of any one of the four; but perfect induction would reason, that what we can prove true of A. B. C. D. separately, we may properly state as true of G., the whole genus. This is evidently a formal argument, as demonstrative as syllogism. But the imperfect or rhetorical induction will perhaps enumerate three only of the species, and then draw the conclusion concerning G., which virtually includes the fourth, or what is the same thing, will argue, that what is true of the three is to be believed true likewise of the fourth.” Newman’s Lectures on Logic, p. 73 (1837). The same distinction between perfect and imperfect induction is made in the Encyclopédie Françoise, art. Induction, and apparently on the authority of the ancients.