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Inductive and Deductive Arguments

  • Page ID
    186196
  • Before we look at what you will be researching and writing on for your advanced research project. It is important we look at some elements of argumentation that we have not addressed. The first of these will be inductive and deductive arguments, and then we will look at bias.

    Inductive and Deductive Arguments

    In this lesson, you will learn to distinguish between and use various forms of logical arguments. It is vital to understand the construction of arguments so that you can both analyze and construct your own.  What makes an argument weak? effective?  Through this lesson, you will learn to spot and analyze both inductive and deductive arguments. Spoting inductive and decutive arguments will help with research as well, so you can spot this in any sources you use.

    Key Terms

    • Argument: a conclusion and the premises that support it
    • Premise: a reason offered as support for another claim (an assumption that something is true)
    • Conclusion: the claim being supported by a premise or premises
    • Valid argument: an argument whose premises genuinely support its conclusion
    • Unsound argument: an argument that has at least one false premise
    • Deductive argument: an argument whose premises make its conclusion certain
    • Inductive argument: an argument whose premises make its conclusion likely
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    To begin to understand, take the oldest example in all of logic, one that Aristotle used in teaching logic at his Academy (the lines are numbered to make it convenient to refer to them):

                1. All men are mortal.

                2. Socrates was a man.

                3. Therefore Socrates is mortal.

     The three lines taken together constitute an argument.  Line 3 is the conclusion. Lines 1 and 2 are premises.

    • Mastering the art of picking out premises and conclusions is the first step toward good analytical thinking, but we must also think about whether the premises really do support their conclusions.  Making that sort of determination requires that we think a little bit about the different kinds of arguments.  There are several ways of categorizing arguments, but for our purposes, we can distinguish all arguments into one of two types: deductive and inductive.

     The difference between deductive and inductive arguments is easiest to see by way of examples.

    •  Smith owns only blue pants and brown pants.  Smith is wearing a pair of his pants today.  So Smith is wearing either blue or brown pants today.

    This is an instance of a deductive argument. We can tell that the argument is deductive because the two premises (that is, the first two sentences) guarantee the truth of the conclusion.  If the two premises really are true, then there is no possible way that the conclusion could be false.  Contrast this example with another example:

    •  January has always been cold here in Siberia.  Today is January 14, so it is going to be another cold day in Siberia.

    This argument is inductive. The premise makes the conclusion likely, but it does not guarantee that the conclusion is true.

    Reflect on how useful inductive and deductive arguments can be when making your own argument and when you are researching. When researching, deductive arguments in any sources you come across are obiviously stronger because they can't be false.