Deductive and Inductive Arguments
What does it mean to suggest that there are different types of arguments? Remember that an argument is an attempt to persuade someone by appealing to one or more premises. There are different types of premises that an argument can use to support its conclusion. Furthermore, there are different types of conclusions that an argument can have. By recognizing the 1- type of conclusion an argument is supporting and 2- the type of premises being offered to support the conclusion, we are better able to describe how an argument is attempting to persuade someone; and this knowledge not only helps us distinguish an argument's conclusion from its premise(s); but, more importantly, it will allow us to evaluate the argument, to determine whether or not the argument's reasons support its conclusion.
What types of arguments are there? Arguments are typically called either "deductive" or "inductive." A deductive argument attempts to provide necessary reasons to support its conclusion. That is, a deductive argument attempts to offer reasons to believe that the conclusion necessarily is true. Consider the following example:
Either John drives or we're going to be late. John isn't driving. So we're going to be late.
If it's true that 1- John drives or we're going to be late AND 2- John isn't driving, then the conclusion -- We're going to be late-- is necessarily is true.
In contrast, an inductive argument attempts to provide probable reasons to accept a conclusion. That is, an inductive argument attempts to offer reasons to believe that the conclusion probably is true. Consider the following example:
The money was in the living room before Jeff went there, and it wasn't there when he left. So he probably took the money.
If it's true that 1- the money was in the living room before Jeff went there, and 2- it wasn't there when he left, then argument is proposing that it's probably true 'Jeff took the money'.
Note that the definitions of deductive and inductive arguments do NOT refer to whether or not the premises are true. Neither do the definitions refer to whether or not the premises are good reasons to believe the conclusion. What makes an argument deductive or inductive has nothing to do with whether or not 1- the premises are true or false or 2- the premises are good reasons to believe the conclusion. To note that an argument is inductive or deductive is to describe the type of support offered in the argument. An argument that attempts to offer necessary reasons to believe its conclusion is an deductive argument. An argument that attempts to infer probable reasons to believe its conclusion is an inductive argument.
In our class we will not be learning deductive arguments. There are two reasons for this. First, the SSU and SRJC Philosophy Departments offer courses in Formal Logic, which focuses exclusively on deductive arguments; so if you wish to learn about deductive arguments there is a course that you can take. Second, my experience suggests that we encounter inductive arguments much more often than deductive arguments; so, our limited time together over this one semester seems better spent learning inductive arguments.
There are two types of inductive arguments that we'll be learning: 1- Inductive Generalizations and 2- Hypothetical Reasoning.