Logic: The Theory of Inquiry  

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Logic: The Theory of Inquiry (1938) is a book by John Dewey.

In it, he explained how modern scientists practice induction and deduction, and why they have no use for natural kinds.

The philosophical issue is how humans can infer one kind of thing from another. The traditional answer grew out of Aristotle's assertion that humans state the kinds they know in two kinds of general propositions. Existential kinds--known by observation--are stated as "generic" general relations. Conceptual kinds--known by reasoning--are stated as "universal" general relations.

Dewey argued that modern scientists do not follow Aristotle in treating inductive and deductive propositions as facts already known about nature's stable structure. They treat propositions as intermediate steps in inquiry, hypotheses about processes displaying stable patterns. Aristotle's generic and universal propositions have become tools of inquiry rather than results.

"Propositions as such are ... provisional, intermediate and instrumental. Since their subject-matter concerns two kinds of means, material and procedural, they are of two main categories: (1) Existential [generic means, known by induction], referring directly to actual conditions, as determined by experimental observation, and (2) ideational or conceptual [universal means, known by deduction], consisting of interrelated meanings, which are non-existential in content ... but which are applicable to existence through the operations they represent as possibilities."

Modern induction starts with a question to be answered or a problem to be solved. It identifies problematic subject-matter and seeks potentially relevant qualities and conditions. Generic existential data thus identified are reformulated--stated abstractly as if-then universal relations capable of serving as answers or solutions.

"No grounded generic propositions can be formed save as they are the products of the performance of operations indicated as possible by universal propositions. The problem of inference is, accordingly, to discriminate and conjoin those qualities [kinds] of existential material that serve as distinguishing traits (inclusively and exclusively) of a determinate kind."

Dewey described these abstract steps concretely with the example of the kind "morning dew." From antiquity, the common sense belief had been that "All dew is a kind of rain," meaning dew drops fall. By the early 1800s the curious absence of rain and the growth of understanding led scientists to examine new qualities. Functional qualities of bodies [kinds] as solid-liquid-gas, and operational constants of conduction and radiation, led to new inductive hypotheses "directly suggested by this subject-matter, not by any data [kinds] previously observable. .... There were certain [existential] conditions postulated in the content of the new [non-existential] conception about dew, and it had to be determined whether these conditions were satisfied in the observable facts of the case.

After demonstrating that dew could be formed by these generic existential phenomena, and not by other phenomena, the universal hypothesis arose that dew forms following established laws of temperature and pressure. "The outstanding conclusion is that inductive procedures are those which prepare existential material so that it has convincing evidential weight with respect to an inferred generalization. Existential data are not pre-known natural kinds, but become conceptual statements of "natural" processes.

"Objects and qualities [kinds] as they naturally present themselves or as they are "given," are not only not the data of science but constitute the most direct and important obstacles to formation of those ideas and hypotheses that are genuinely relevant and effective."

"We are brought to the conclusion that it is modes of active response which are the ground of generality of logical form, not the existential immediate qualities of that which is responded to."

"Dewey concluded that nature is not a collection of natural kinds, but rather of reliable processes discoverable by competent induction and deduction. Assuming kinds to be given leads to the error of assuming that conceptual universal propositions can serve as evidence for generic propositions; observed consequences affirm imagined causes. "For an 'inference' that is not grounded in the evidential nature of the material from which it is drawn is not an inference. It is a more or less wild guess." Modern induction is not a guess about natural kinds, but a means to create instrumental understanding."