Rational persuasiveness

It is plain common sense that the role of an argument is to give us reasons for accepting its conclusion as true. But we have not quite defined what it is, exactly, for an argument to do this. You might think that we have done this with the notions of deductive and inductive soundness, but that is not quite right. The reason is that even if we have reconstructed an argument perfectly, we cannot always tell whether or not the argument is sound. And that is because a sound argument must have true premises. A deductively sound argument is one that has true premises and which is deductively valid; an inductively sound argument is an inductively forceful argument with true premises. Since we do not always know which propositions are true and which false, we cannot always tell whether an argument is sound or not.

What we want, rather, is to characterise the property of 'giving us good reasons to accept the conclusion' in such a way that when an argument has that property, we are always able to recognise it - just by virtue of whatever knowledge we do possess, along with our ability to assess arguments logically. This property cannot be the property of validity or inductive force, since the fact that an argument is valid or forceful does not give us a reason to accept its conclusion unless we already have reason to accept the premises. But neither can this property be the property of soundness, since being able to recognise that normally requires that we have factual knowledge that goes far beyond the ability to analyse or reconstruct arguments.

Here is a very simple illustration. Suppose you are wondering whether or not you should expect that interest rates will increase in the next year, and someone presents you with the following argument:

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