# Introduction

Writers use logical order when they want to persuade their readers to believe or do something. They will make a claim (thesis) and support it either deductively or inductively. In a deductive argument, the claim comes before the evidence, and in an inductive argument, the evidence comes first. Recognizing the logical order of an argument helps you judge the validity of the argumentative essay and whether you agree or disagree with the writer.

In his deeply philosophical book Zen and the Art of Motorcycle Maintenance: An Inquiry into Values, Robert Pirsig describes a cross-country motorcycle trip he makes with his son Chris. Throughout the journey, he engages his son in numerous discussions about the meaning of life and how to make sense of the world around us. At one point, his motorcycle starts having engine problems, and he uses the situation to explain inductive and deductive reasoning to Chris.

If the cycle goes over a bump and the engine misfires, and then goes over another bump and the engine misfires, and then goes over another bump and the engine misfires, and then goes over a long smooth stretch of road and there is no misfiring, and then goes over a fourth bump and the engine misfires again, one can logically conclude that the misfiring is caused by the bumps. That is induction: reasoning from particular experiences to general truths.

Deductive inferences do the reverse. They start with general knowledge and predict a specific observation. For example, if, from reading the hierarchy of facts about the machine, the mechanic knows the horn of the cycle is powered exclusively by electricity from the battery, then he can logically infer that if the battery is dead the horn will not work. That is deduction.

Source: Triumph T 110 650 cc motorcycle from 1954, Pierotreruote, Wikimedia Commons

Before you begin the following exercises, think of the ways you go about persuading people to do what you want. Sometimes a direct approach works best. For example, let’s say you want to go sailing, so you check the weather report. You learn that today will be perfect sailing weather, but tomorrow will be stormy and cold. You call a couple of your friends and say, “We’re going sailing today,” and then you give the reasons why after making this statement. Because you don’t have much time, you don’t want to waste it by having to persuade your friends. You decide that a direct approach to planning your day works best. This is an example of deductive reasoning.

Other times might require a softer, more indirect approach, such as when you try to get your parents to give you permission to do something they might not want you to do. For example, you might want to go on the school band trip to Orlando over Spring Break. Instead of walking in and announcing to your parents, “I am going on the band trip to Orlando,” you remind them of how responsible you are, how much money you have saved from your part-time job, how much the band and your friends mean to you, etc., and then, using a more conciliatory approach you say, “I think it’s a good idea for me to go on the band trip to Orlando.” This is an example of inductive reasoning.

Sometimes it’s difficult to separate these two types of reasoning because we often use them together; drawing conclusions in inductive reasoning is likely to lead to the premises in deductive reasoning. Also, inductive reasoning is uncertain even though it’s our way of knowing anything about the real world. Deductive reasoning is certain but very artificial, yet it governs the way we think, reason, and communicate.