According to research in cognitive science,
most human beings earn a failing grade in elementary logic. But we’re not just frequently incompetent, we’re also willfully and skillfully illogical. When a piece of deductive reasoning leads to a conclusion we don’t like, we often rebut it with irrelevancies and sophistries of which, instead of being ashamed, we act proud. Recently, a new mortality study … reported that … the death rate among smokers was twice as high as that among nonsmokers. That night on television … a reporter was shown asking various smokers what they thought of the findings: one man sarcastically replied, “So nonsmokers don’t die, right?”—and looked immensely pleased with himself; a young woman, with equal self-satisfaction, said, “Nobody lives forever, anyway.” Such rebuttals are not at all unusual; many psychological studies have shown that smokers tend to reject logical inferences about smoking by means of various distortions and rationalizations. They may assert that the evidence is incomplete or biased, or cite the case of someone they knew who smoked heavily and lived to be ninety, or, like the man and woman on television, rebut conclusions other than the one that was actually drawn.
Similarly, most people are little influenced by the reasoning, however cogent, of campaigners, organizers, and other public persuaders. Jeanne B. Herman of the Graduate School of Management at Northwestern University has studied the reactions of people subjected to company and union arguments prior to voting on some issue, and found that few of them change their attitudes as a result of such exposure. By a variety of nonlogical cognitive techniques they “insulate” themselves from the reasoning they are exposed to unless it confirms their preexisting attitudes. To be sure, some part of every voting population changes its views in the course of a campaign, but the cause of shifts are factors such as personalities of the campaigners, changing economic conditions, threats or promises, and so on; the noble ideal of persuasion by means of the clash of ideas in the marketplace has little to do with it.
Even within the ranks of foreign-policy decision makers, rationality is the ideal but rarely the reality. The classic theory of high-level decision making views it as a process in which the theoretical rational man weighs costs against benefits and inexorably comes to the optimal decision, but many recent studies find that this is rarely the case. Political scientists Ole R. Holsti of Duke University and Alexander George of Stanford University have analyzed various examples of such decision making and found that only when a problem is trivial do foreign-policy decision makers behave rationally; far more often, such factors as stress, the complexity of the problem, and their own conflicting motives cause them to make decisions by irrational processes...
If we need any final piece of evidence that even fine minds are not so much let by logic as prone to bend logic to their own conclusions, look at the output of the United States Supreme Court…. The justices interpret the language of the Constitution in their own ways, so as to derive from it justification for their own social values. As [former] Chief Justice Charles Evans Hughes said to William O. Douglas, when Douglas was new to the Supreme Court, “You must remember one thing. At the constitutional level where we work, ninety percent of any decision is emotional. The rational part of us supplies the reasons for supporting our predilections.”
Thus there is yet another paradox about the human ability to reason deductively: those who are best at logical reasoning often use it—as the rest of us use illogic—to get where they want to go, rather than where reason would naturally lead them. [Morton Hunt, The Universe Within, 128-130]
What cognitive science has discovered in research accords with the experience of everyday life. Anyone who attempts to change people’s minds on any issue that is important to them will quickly find how difficult it is. The reason for this is quite simple: most people make up their minds based on their sentiments, and so they are impervious to logic. It is Pareto’s “residues” that are critical in determining belief and conduct, not the theories of philosophers and social thinkers, which are mere “derivations.” As Pareto himself puts it:
Theologians, metaphysicists, philosophers, theorists of politics, law, and ethics, do not ordinarily accept the order indicated [of residues being more important than derivations]. They are inclined to assign first place to derivations. What we call residues are in their eyes axioms or dogmas, and the purpose is just the conclusion of logical reasoning. But since they are not as a rule in any agreement on the derivation, they argue about it till they are blue in the face and think that they can change social conditions by proving a derivation fallacious. That is an illusion on their part. They fail to realize that their hagglings never reach the majority of men, who could not make head or tail to them anyhow, and who in fact disregard them save as articles of faith to which they assent in deference to certain residues. [Mind and Society, §1415]