correlation does not prove causation, no correlation DOES prove no causation. ( )

Dr. Anthony Flew, emeritus professor of philosophy, taught at Reading University in England for nine years. He had a distinguished teaching career. He lectured at Christ Church, Oxford and University of Aberdeen and taught 20 years at the University of Keele, the same placed he received his doctorate, prior to teaching at Reading University. Upon retiring from Reading he assumed a part-time teaching position at York University in Toronto. He has written over twenty books related to philosophy.

Dr. Flew wrote “How to Think Straight,” to enable people to become better thinkers by examining primarily bad examples of thinking from a vast array of thinkers both past and present. If one is interested in sorting through information in a critical way, then this book provides a framework and many examples toward clarifying one’s thinking.

The book begins by identifying some of the key terms necessary for one to logically think through the information presented throughout the entire book. Some of the key terms Flew describes are propositions, which are either true or false, and arguments, which are valid or invalid. The clarifying of terms is crucial in order for one to decide on the validity or invalidity of an argument. Flew makes a distinction about his book that it is “not about theoretical logic but about logic coaching,” therefore, his book is more of a guide than a textbook, which at times, may make it difficult for a reader not well versed in logic to comprehend the point he is trying to make.

He discusses the difference between generalizations, “some men are mortal,” and universal propositions, “all men are mortal.” The importance of distinguishing the meanings of crucial terms is vitally important in logic. Equivocation is a fallacy in logic where terms in the proposition are ambiguous and used in different ways. One can have a valid argument with false premises and a false conclusion or with a false premise and a true conclusion just as one can have an invalid argument with a conclusion that is true. Flew lays the framework in the beginning to enable one to determine the validity of arguments.

The second chapter provides an array of examples to demonstrate the hypothetical syllogisms. Affirming the Antecedent “if p then q, p, therefore q” and Denying the Consequent “if p then q, ~q, therefore ~q,” are the two valid forms whereas Affirming the Consequent, “if p then q, q, therefore p,” and Denying the Antecedent, “if p then q, ~p, therefore ~q,” are invalid forms. Universal propositions are impossible to prove with finality because the proposition encompasses all of a certain group and it takes only one dissenting example to prove the proposition false. Flew gives ample space to demonstrating with several examples of the invalid argument of denying the antecedent.

Flew develops the concept of a logically necessary condition, which insists that a second proposition’s truth is dependent upon the first proposition’s truth. A logically sufficient condition, insists that the first proposition’s truth is dependent upon the second proposition’s truth. A causally necessary condition indicates that for one thing to occur another must occur first, while a causally sufficient condition indicates that if one condition is present then a second condition is guaranteed.

Flew touches on the square of opposition by introducing two valid contradictory propositions. Their symbolic forms are “all s is p” and “some s is not p,” and “no s is p” and “some s is p.” He also introduces the contrary proposition, “all s is p” and “no s is p.” Understanding these types of propositions can help one think straight by providing a way to counter another’s proposition.

A contradictory is a pair of propositions which are both true only if the other is false, illustrated symbolically like this, “all s is p and some s is not p” or “no s is p and some s is p.” A contrary is a pair of propositions where both can be false but cannot both be true.

Flew introduces his “No True Scotsman” example and explains the concept of falsifiability, which in a proposition it is possible to describe a circumstance that if one demonstrated the occurrence of that circumstance the proposition would then be false. He discusses additional forms of arguments and some key terms to help one sort through arguments in a more critical way. An a priori argument for example, is independent of the senses and reasons deductively from abstract to general. Necessary truth of this kind is determined by reason. An a posteriori argument is dependent on information derived from the senses. Contingent truth of this kind is determined by a reference to something else. A logically necessary proposition cannot be denied without being contradictory, whereas a logically contingent proposition is either true or false but could have potentially been different.

The subject/motive shift is addressed by Flew in chapter four. This tactic shifts the focus from the subject of the argument at hand to the motive of the one presenting the argument. He distinguishes between three meanings of reason, which are grounds, motive and cause. The “on-your-own-principles maneuver” is the proper pointing out of the eventual outcomes of an opponent’s argument.

Language plays a pivotal role in thinking correctly, for how can one think correctly if one is unclear about what to think about. Vagueness in language is words or phrases that lack precise meaning. Ambiguity in language is caused by the presence of two or more meanings for a single word. Definitions of words are important but not always necessary. One only needs to define terms if their meanings may be unclear from the context.

Statistics are used to prove a point in many segments of society. Flew calls for an “unspecialized critical alertness” in our examination and use of statistics. Factors such as the origination of the statistics, the principles used in compiling the statistics, faulty comparisons, and reporting some or all the statistics gathered can skew or appropriately represent the facts. Common misunderstandings of families, women, money, poverty, and crime arise from the use of figures in ways that slant meanings inappropriately. Many people present statistics to convince one toward their point of view so it is necessary to be critical of statistics and beware of taking them at face value if there is scant qualifying information.

Flew concludes by examining several more fallacies and exposing one to faulty arguments, which challenges one to become an improved critical thinker. It is wrong to include assumptions in a question such as, “When did you stop beating your wife?” Another important distinction is to discern the different uses of “experience” which can be either objective or subjective. The genetic fallacy is one in which one argues “that the antecedent must be the same as their fulfillment.” Flew also discusses the black and white fallacy that says there are no gradations of degree. Something is either this extreme or that extreme and allows for no gray areas. Advertisers often use percentages to sell their products and it is vitally important for one to ask what the percentage is relative to. The naturalistic fallacy is also discussed, which mistakenly associates something morally good with something natural.

Learning to think straight involves diligence and critical assessment of ideas. Reading and utilizing the critical reasoning skills discussed in this book will enable one to begin the journey of thinking straighter. One must be willing to admit and learn from mistakes, which are inevitable, and live the examined life in order to pursue the knowledge of the truth.