Often it is reasonable to accept a claim as true even in the absence of any arguments for or against it. For example, suppose you are in a restaurant, and the waiter says ‘I’m sorry, there is no more barramundi tonight.’ Usually it would make sense to take the waiter’s word for it, and accept that you did, in fact, miss out on the barramundi. Put another way, your basis for accepting that the barramundi is all gone is simply the waiter’s assertion to that effect.

Notice that the waiter’s assertion is not an argument. In saying that ‘there is no more barramundi tonight’ the waiter has not provided any evidence that there is no more barramundi; he has simply said that there is none.

Figure 2.10

More generally, assertion by another person is one of many kinds of non-argumentative

bases you might have for accepting a claim.

    A basis is any source of rational support for a claim other than

    a reason or objection.

Other bases include expert opinion, personal experience, common belief, example, publication, and by definition.

Evaluating Bases

Although bases are not arguments, they can be evaluated in terms of the extent to which they provide rational support for a claim. For example we can evaluate assertions as bases for the asserted proposition. We might accept that there is no more barramundi because the waiter said so, but no thoughtful person would accept that global warming is uncertain because an oil industry lobbyist said so.

We normally evaluate arguments in terms of strength. We could, similarly, talk of bases as being more or less strong, but this would be muddying the waters, since bases and arguments are somewhat different in nature. A suitable alternative is to evaluate bases as having degrees of solidity – solid, shaky, worthless etc.

When judging the solidity of a basis, we should use criteria appropriate to that basis. For example, the solidity of an assertion as a basis turns on issues such as: Is the person making the assertion reliable? Is he being sincere? Does he know what he is talking about?

Converting Bases into Arguments

It is always possible to convert a basis into an argument, by articulating it explicitly in the form of a claim or claims. Thus I can accept that there is no more barramundi on the basis that the waiter said so; or, I can construct for myself an argument such as the one below. Notice that the criteria for evaluation of the basis make an appearance in the premises of the argument.

Figure 2.11

Regresses and Terminals

Bases address a profound issue in the evaluation of arguments. We often hear the supposed principle that a critical thinker only ever accepts claims on the basis of good arguments. However, this cannot always be true, for it creates what philosophers call an infinite regress. Arguments are made up of premises, which must be accepted if the arguments are to provide any support. Hence, if we subscribe to the principle, we must look at the arguments for those premises, and so on forever.

It appears that the critical thinker would never get to accept anything, because she would never complete the infinite task of investigating all the arguments. The regress can only be broken if there are situations in which we can reasonably accept claims as true without investigating further arguments. This is where bases come in; they allow us, provisionally at least, to rationally accept claims in the absence of explicit arguments. They are stopping points or terminals in the process of determining whether a claim has rational support.