Key terms and concepts
Observations on the way terms are being used in this course and on how to avoid common errors.
Arguments in Action
Deductive arguments
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Distinction A Deductive arguments are those whose premises are general and whose conclusion is particular, whereas Inductive arguments are those whose premises are particular and whose conclusion is general. |
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Distinction B "A deductive argument is an argument whose conclusion follows necessarily from its basic premises. More precisely, an argument is deductive if it is impossible for its conclusion to be false while its basic premises are all true. An inductive argument, by contrast is one whose conclusion is not necessary relative to the premises: there is a certain probability that the conclusion is true if the premises are, but there is also a probability that it is false." Schaum's Outlines: Logic p23 |
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Distinction C A deductive argument is one that makes the claim that if the premises are true, then the conclusion is guaranteed to be true. A non-deductive argument is one that makes the claim that if the premises are true, then the conclusion is likely to be true. or
Harrell p24 (emphasis added) |
Distinction A was once the traditional distinction but as long ago as 1994 George Bowles was able to describe this distinction as "almost universally discarded." There is more than one reason for rejecting this distinction but simple consistency is the most obvious. Consider the following:
Aberdeen is north of Edinburgh and Edinburgh is north of London. Therefore, Aberdeen is north of London.
Everyone wants to accept this as a deductive argument but it doesn't fit with distinction A. These kinds of counterexamples can be multiplied very easily. The SQA has made it very clear in the marking instructions for 2017 and 2018 and in the corresponding course reports that this definition will not be accepted.
The problem with distinction B is that it equates a deductive argument with a deductively valid argument. The definition of 'deductive' and 'valid' is the same. This means that it is not possible to have a 'bad' deductive argument any more than it is possible to have a bad valid argument. The distinction also means that all arguments are either deductive or inductive so any argument that isn't valid is inductive. According to this distinction the formal fallacies end up being classified as inductive arguments. In addition, it follows that the term 'invalid' cannot apply to deductive arguments and being invalid is a feature, and only a feature of, inductive arguments. Although the mandatory documents do not address this issue it is clear from past documents (e.g. the 2010 Course Specification) that the convention being followed by the Higher Course is that the valid/invalid distinction is something that applies to deductive arguments.
Distinction C is not without its problems, most notably that it isn't always possible to know what the arguer intended, nevertheless, even though it isn't clearly stated in the current mandatory documents, this is the distinction that the Higher Course has been using. The mandatory requirements for the previous version of the Higher published in 2010 stated that a deductive argument "attempts to draw certain conclusions from premises" and an inductive argument "attempts to draw probable conclusions from premises".
It is worth noting that Harrell distinguishes between deductive and non-deductive arguments rather than between deductive and inductive arguments. For more on this see inductive arguments.