All dogs have four legs.
My cat has four legs.
Therefore, my cat is a dog.

This is the kind of reasoning that, when put in concrete examples such as this, makes little sense. But when it is applied to business, political, military and other types of situations, it becomes less clear, because the substance of the argument is less clear.

All military objectives require White House approval.
The education budget requires White House approval.
Therefore, the education budget is a military objective.

McInerny writes with good prose and good style in presenting in gentle and humourous form the elements of making sense. Being logical is about good communication, and this requires first and foremost clear, unambiguous and direct speech (given these criteria, I wonder why political speech often suffers from logic problems?).

McInerny develops a long section on argumentation - problems and situations about comparison, conditionals, moving from universals to particulars and vice versa, truth, value, fact, inductive and deductive argumentation and more. From this basic format (which really hinges on the simplest of platforms, that an argument contains a premise and a conclusion), McInerny proceeds to examining the sources and forms of illogical thinking (bad reasoning). Some of these are common sensical - evasiveness, cynicism, skeptism, emotionalism: any of these taken to extremes (or sometimes just a bit beyond moderation) can cause flaws with argumentation. According to McInerny, common sense is 'characterised by the unfailing capacity consistently to distinguish between a cat and a kangaroo.' Logic, common sense and good reasoning rely upon language that reveals, not conceals, and 'is suspicious of words that dazzle more than denote.'

McInerny presents a long litany of typical faulty-logic types that nonetheless are commonplace. These include very familiar types (straw man arguments, begging the question, ad hominem fallacies) as well as less familiar but more insidious types (misclassification, affirming the consequent, denying the antecedent, reductionism). He also looks at problems that are less 'logical' as they are problematic for continuing argumentation and debate - laughter and tears (both unlike to show up in logical constructions on paper) can both be used as diversionary tactics in the process of logical discussion.

'Important though it is to avoid the pitfalls of poor reasoning, it is more important to concentrate our energies on mastering those positive principles that make for its happy opposite - sound reasoning.' McInerny appeals to philosophers such as Aristotle in his constructions, but does not present dry and dusty prose - his writing is fresh and accessible, interesting to follow and helpful for people in all walks of life.