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Ch. 3: Logic and Critical Thinking | Rationality

Please use this thread for discussing Ch. 3: Logic and Critical Thinking | Rationality.

This chapter starts with dissecting several arguments with formal logic.

...we need to add another conditional, "If the smartest people in the world predict something, it will come true." But we know this conditional is false. Einstein, for example, announced in 1952 that only the creation of a world government, P, would prevent the impending self-destruction of mankind, Q (IF NOT P THEN Q), yet no world government was created (NOT P) and mankind did not destroy itself (NOT Q; at least if "impending" means "within several decades").

However, in the following section he discusses less formal analysis.

Critical Thinking and Informal Fallacies
...Rather than crisply violating an argument form in the propositional calculus, arguers exploit some psychologically compelling but intellectually spurious lure. They are called informal fallacies, and fans of rationality have given them names, collected them by the dozens, and arranged them (together with the formal fallacies) into web pages, posters, flash cards, and the syllabuses of freshman courses on "critical thinking."

Pinker goes on to list and discuss some of these familiar fallacies such as strawman, argument from authority, ad hominem, etc. He says Wikipedia lists more than a hundred, not sure if this is what he is referring to.

I'm not sure what Pinker thinks about the differences between formal logic (Ps and Qs) and informal fallacies (guilt by association). He seems to say formal logic rules, but is not practical, yet informal methods are not reliable. What do you see?

Chapter Three, on logic, includes a remarkable quotation from the great seventeenth century philosopher of the enlightenment, GW Leibniz, co-inventor with Newton of calculus. Leibniz said a universal language of logic “will be the greatest instrument of reason,” for “when there are disputes among persons, we can simply say: Let us calculate, without further ado, and see who is right” (The Art of Discovery (1685); C 176/W 51).

This suggestion, which Pinker calls a fantasy of epistemic utopia, is easy to mock, in view of how distant our society is from such pure rationality. Twenty years ago, British Prime Minister Tony Blair expressed a similar attitude to Leibniz by calling for government policies to be based on evidence. At first blush that seems a perfectly logical thing and a worthy goal. The problem is that we are never in possession of sufficient information to determine our decisions without reference to some abiding principles of judgement. Again, this confronts Hume’s argument that we can’t derive an ought from an is, or a value from a fact. Our values are the complex product of experience, and are never simple matters of calculus as Leibniz would have it.

Disputes raise the inevitable problem of predicting the outcome of alternative paths. The entirety of law, politics and business run up against this problem of the impossibility of separating the true and false prophets in advance. The results of the Leibniz attitude are seen in the challenging story of efforts to base social policy on scientific knowledge, the idea that pure logic can determine what we should do.

When critical thinking is fetishized, a la Leibniz, a number of problems arise. Pinker starts by observing the Dr Spock alien attitude of contempt for foolish emotion, a running joke in Star Trek. He then goes through a series of problems in logic, to show how easy it can be to ignore our false assumptions and accept fallacious and unsound reasoning. Political debate routinely sways opinion in this way, using invalid premises and assumptions.

The Enlightenment philosophy of Leibniz laid a genetic path toward modern secular rationality. Along the way, the communist movement portrayed itself as “reason in revolt”. It can be very interesting to analyse the history of rationalism, as it helps to inform some modern political and social debates. To just pick a few of the most prominent, climate change, education, religion, taxation, the role of government, are all policy questions that are stymied by conflicting views about what is reasonable.