In this post, I discuss a dialectical norm that's often violated in the apologetics literature (though of course apologists don't have a corner on the market for this fallacy or any other). First, though, some stage-setting.There are three main propositional attitudes or "stances" one might take with respect to a given proposition, P:
1. Statements, Stances, and Evidence
1. Statements, Stances, and Evidence
(i) Believe that P is true.
(ii) Believe that P is false, i.e., believe that ~P is true.
(iii) Suspend judgment with respect to P: neither believe that P is true nor believe that ~P is true.
The epistemically appropriate stance for one to take with respect to P is a function of the evidence one has with respect to P. Thus, if one's basic or non-basic evidence at least slightly favors P, then one rationally ought to believe that P is true, where the strength of one's belief is proportioned to the strength of the evidence for P; if one's evidence at least slightly favors ~P, then one rationally ought to believe that P is false, where the strength of one's belief is proportioned to the strength of the evidence against P; and if one's evidence favors neither P over ~P, nor ~P over P, then one ought to suspend judgment about whether P is true, neither believing P nor believing ~P.
2. Defeaters and Dialectical Context
Now consider the following common dialectical context: person A asserts to another person B that statement P is true, and points B to basic or non-basic evidence E in support of P. In this context, unless B has an independent, outweighing reason to believe that P is false or unjustified (note the important qualification), B has at least some reason to adopt the stance of belief over the stances of disbelief and suspension of judgment with respect to P.
However, B loses such a reason to believe that P is true -- a reason to retain the stance of suspending judgment about P or believing that ~P -- if B has a defeater for P -- i.e., an independent reason for thinking that P is false or unjustified. Now there are two main types of defeaters: rebutting defeaters and undercutting defeaters. A rebutting defeater for P provides one with a reason to think that P is false. By contrast, an undercutting defeater merely neutralizes one's evidence for the truth of P. A common form of undercutting defeater for P is a live epistemic possibility (i.e., a scenario that one's evidence can't rule out as false or unjustified) that, if true, entails that P is false.
We’ve just seen that (absent other reasons for P) a rebutting defeater for P gives one a reason to believe that ~P, and an undercutting defeater gives one a reason to suspend judgment with respect to P. An important implication of this is that a defeater D may fail to show that P is false, and yet succeed in indicating a live epistemic possibility that's incompatible with the truth of P. In such a case, D succeeds in showing that B ought to suspend judgment about the truth of P, even though D fails to show that B ought to believe that P is false.
Given the frequency of such dialectical contexts, the point is worth belaboring: from the fact that D fails as a rebutting defeater for P, it doesn't follow that D fails as an undercutting defeater for P. Therefore, if a person A asserts that P is true, and another person B offers D as a defeater for P, it's not enough for A to show that D fails to show that P is false; A must also show that D fails to neutralize the evidence for P.
3. Dialectical Norms, Dialectical Fallacies, and a Common Apologetic Fallacy
The previous points put us in a position to understand an important dialectical norm in the context of assertions. Thus, consider the following dialectical context: A believes that P is true, B does not believe P is true or justified, and A is trying to rationally persuade B that P is true. Toward this end, A offers evidence E for P. Now suppose that B considers E, but on reflection becomes aware of a defeater D for P. Finally suppose that A replies by showing that D fails to show that P is false. Should B therefore believe that P is true?
Not necessarily. For as we’ve seen, it may be that D fails as a rebutting defeater for P, and yet succeeds as an undercutting defeater for P. That is, even if A shows that D fails to indicate that P is false, A might yet fail to rule out D as an undefeated, live epistemic possibility that's incompatible with the truth of P. But if so, then even if B ought not believe that P is false, B nonetheless ought to suspend judgment about P.
The preceding discussion reveals a dialectical norm: in dialectical contexts of the sort sketched above, a person in A's position must not only show that (i) D fails as a rebutting defeater for P, but also that (ii) D fails as an undercutting defeater for P. And to assume that A discharges their dialectical obligations in offering justification for P to B in such contexts by accomplishing (i) alone is to commit a certain sort of dialectical fallacy.
The fallacy sketched above occurs so frequently in the apologetics literature that I hereby label it the Apologetics Fallacy. The Apologetics Fallacy is the dialectical fallacy that occurs when one assumes, in contexts of the sort sketched above, that because one has shown that D isn't a rebutting defeater for P, one has thereby shown that D isn't an undercutting defeater for P. A paradigm case of the Apologetics Fallacy can be found on pp. 291-292 of this article. And a paradigm case of the appropriate response to the Apologetics Fallacy can be found on the same pages of the same article.