Writing Analytically, 6th Edition - Rosenwasser, David & Stephen, Jill.original_ [210]
—Bruce Wightman, Professor of Biology
B. The Shaping Force of Common Thought Patterns
DEDUCTION AND INDUCTION
According to the usual definitions of the terms deduction and induction, you might expect that a fairly full-fledged version of the thesis would appear at the beginning of a deductive paper but at the end of an inductive one. But as we will go on to show, papers don’t neatly fit these two abstract models of thinking. In practice, all writing combines the two patterns. In virtually all essays, the paper begins with some kind of organizing claim; this is not delayed until the end. And in virtually all essays, the opening claim is not simply repeated at the end but occurs there in its duly tested and evolved form. To clarify these claims we need to offer some definitions. (See Figure 15.1, A and B).
FIGURE 15.1 Deduction and Induction.
Deduction (A) uses particular cases to exemplify general principles and analyze their implications. Induction (B) constructs general principles from the analysis of particular cases. In practice, analytical thinking and writing blend deduction and induction and start either with particular cases (C) or a general principle (D).
Deduction
As a thought process, deduction reasons from a general principle (assumed to be true) to the particular case. It introduces this principle up front and then uses it to select and interpret evidence. For example, a deductive paper might state in its first paragraph that attitudes toward and rules governing sexuality in a given culture can be seen, at least in part, to have economic causes. The paper might then apply this principle, already assumed to be true, to the codes governing sexual behavior in several cultures or several kinds of sexual behavior in a single culture.
A good deductive argument is, however, more than a mechanical application or matching exercise of general claim and specific details that are explained by it. Deductive reasoning uses the evidence to draw out the implications—what logicians term inferring the consequences—of the claim. The general principle explains selected features of particular cases, and reciprocally, the evidence brings out implications in the principle.
Thus, the general principle stated at the beginning of the paper and the idea stated as the paper’s conclusion are not the same. Rather, the conclusion presents the (evolved) idea that the writer has arrived at through the application of the principle.
Induction
An inductively organized paper typically begins not with a principle already accepted as true but with particular data for which it seeks to generate some explanatory principle. Whereas deduction moves by applying a generalization to particular cases, induction moves from the observation of individual cases to the formation of a general principle. Because all possible cases can obviously never be examined— every left-handed person, for example, if one wishes to theorize that left-handed people are better at spatial thinking than right-handers—the principle (or thesis) arrived at through inductive reasoning always remains open to doubt.
Nevertheless, the thesis of an inductive paper is generally deemed acceptable if a writer can demonstrate that the theory is based on a reasonably sized sampling of representative instances. Suffice it to say that a child who arrives at the thesis that all orange food tastes bad on the basis of squash and carrots has not based that theory on an adequate sampling of available evidence.
The Overlap
In most cases, induction and deduction operate in tandem (see Figure 15.1, C and D).