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All about reality
on 22 March 2012
A superb guide to straight thinking by D. Q. McInerny, short enough for an afternoon's diversion, significant enough for its lessons to last a lifetime. I'm pretty sure that few of us as children wanted to be logical when we grew up. We wanted to be liked, loved, to have a laugh - but logical? Even sensible grownups rarely include being logical on their list of aspirations. McInerny's direct and clear style of writing, his avoidance of jargon and appeal to simple examples all combine to draw the reader into a subject that may seem a million miles away from everyday concerns. His first success is to remind us that logical thinking is a normal part of ordinary thinking, something we do all the time and even take for granted (until it goes wrong). He then sharpens our skills and deepens our appreciation of the subject. His greatest achievement, perhaps, is to show how being logical is a good thing in itself, an essential part of being human: the "art of logic is like no other, for it goes to the very core of what we are".
It's not only mathematicians or rocket scientists who need logic in their working lives, and it's not just in our working lives where logical thinking is important. McInerny suggests that "the first principles of logic" and "the first principles of human reason" amount to the same thing. Indeed, for much of the time being logical comes perfectly naturally. We don't need to read a book on critical thinking to know that if Jim is in London he cannot also be in Oxford. Most of us would easily recognize and reject a contradictory statement that claimed that Jim was both in London and in Oxford at the same time. Where a book like McInerny's is important and fascinating is in sketching out the bigger picture, showing the connections between several familiar ideas.
Part One is "Preparing the Mind for Logic" but might as well be called "Preparing the Mind for the Day Ahead" so fundamental is its content. Words like "fact", "idea", "truth" and "word" itself are so commonplace that we can easily forget how deep are the assumptions that underpin them. That there is a world out there, existing independently of our minds; that this world contains things and events, which can both become facts corresponding to ideas in the mind; that these ideas can be described by words; that language can reliably communicate these ideas from one mind to another; that knowledge about the world can thereby be compiled and maintained over time.
A contradictory statement "in effect speaks against itself, for it is saying something that does not correspond to the objective facts". The avoidance of contradiction is therefore "simply the avoidance of falsehood". Objectivity, facts, truth, falsehood - almost without realizing it, suddenly we're dealing with that most basic and often elusive thing: human knowledge. McInerny keeps it simple (I don't think he even uses the word "epistemology"), and lists the three basic components: an objective fact (e.g. a cat), the idea of a cat, and the word we apply to the idea (e.g. "cat").
This shows how "logic and language are inseparable" and how being logical "presupposes our having a healthy respect for the firm factualness of the world". Language allows us to describe that world, and anyone who values language ought also to value logic. We should be wary of anyone who scorns logic while at the same time glorifying language as if it were the sole guide to truth. They may be trafficking in bad ideas, which have ceased to faithfully reflect the objective world. (Bad ideas can still be informative - "about the subjective state of the persons who nourish those ideas".)
While words are important in describing ideas, "it is the statement that logic starts with, for it is only at the level of the statement that the question of truth or falsity is introduced, and logic is all about establishing what is true and distinguishing it from what is false". It would be meaningless to enquire whether or not the words "dog" and "garage" are true or false, but if we combine them into a simple statement -- "the dog is in the garage" - then either "true" or "false" is the appropriate response.
More tricky is the evaluative statement - "that dog is ugly" - since "it combines both subjective and objective elements". Evaluative statements are open to argument, since they "do not lend themselves to a simple true-or-false response". (Statements of objective fact, so long as they are true, are not open to argument.)
The remaining parts of the book cover the basic principles of logic, argument, the sources of illogical thinking, and the principal forms of illogical thinking (a long list of fallacies). The delicious thing about stripping fallacies down to their bare essentials is that while you're wondering how on earth anyone could make such a blunder you're also remembering all those examples of when a politician or a businessman or you yourself did just that. As McInerny says of one particular fallacy, it's "a pretty obvious mistake to claim that something is necessarily true for a whole group because it happens to be true for a part of the group" - and yet it happens all the time, and easily qualifies as one of the human family's favourite fallacies.
Public health initiatives and the owners of private gyms are forever encouraging us to exercise our bodies. Some exercise is essential, of course, although no one seems to agree on just how much. When it comes to exercise for the mind, I would recommend McInerny's "Being Logical" over puzzles or mental arithmetic. While few of us will ever do much more than jog around the park, most of us are more than capable of being logical, especially with the help of books like this.