If one maintains that for any set of conditions X that one proposes as constitutive of S's justification for believing P, those conditions must always be fortified with some other set of conditions describing S's access to X, then the view is hopeless. Call the satisfaction of access conditions to X, A1. Will X together with A1 constitute justification for S to believe P? Not given the view. Our strong access requirements require access (call it A2) to the new proposed sufficient conditions for justification (X and A1). But the conjunction of X, A1, and A2 will not constitute S's justification for believing P as the view requires us to add access to these conditions and so on ad infinitum.
To avoid this problem, the strong access internalist must distinguish carefully a view about what is constitutive of justification from a view about what is necessary for justification. If the view is to be intelligible the access internalist must argue that when some set of conditions X constitutes S's justification for believing P, those conditions will be such that they entail that S has access to them. The access, however, need not be part of what constitutes the justification. An analogy might be helpful. P cannot be true unless it is true that P is true - P's truth entails (in some sense of "entails") that it is true that P is true. But it would be a serious mistake to argue that P's being true is constituted by its being true that P is true. The correct analysis of what it is for P to be true should not make reference to metatruths about P's truth even if the correct analysis of P's being true must reveal why P's being true entails that it is true that P is true.
Laurence BonJour (1985) raised another highly influential objection to all forms of classical foundationalism (an objection raised before he joined the ranks of foundationalists). The objection presupposed a strong form of what we might call access internalism. Put very superficially the access internalist argues that a feature of a belief or epistemic situation that makes a belief noninferentially justified must be a feature to which we have actual or potential access. Moreover, we must have access to the fact that the feature in question is probabilistically related to the truth of what we believe. So suppose some foundationalist offers an account of noninferential justification according to which a belief is noninferentially justified if it has some characteristic X. BonJour then argues that the mere fact that the belief has X could not, even in principle, justify the believer in holding the belief. The believer would also need access to (justified belief that!) the belief in question has X and that beliefs of this sort (X beliefs) are likely to be true. At least one of these propositions could only be known through inference, and thus the putative noninferential justification is destroyed.
BonJour presented the objection on the way to developing a coherence theory of empirical justification. But it ultimately became obvious that the objection to foundationalism, if good, was too strong. Given the structure of the argument it should become evident that the coherence theory (and any other theory) would be equally vulnerable to the argument. Just replace “X” with some complicated description of beliefs cohering with each other. That might suggest to the classical foundationalist that strong access internalism is a view to be avoided. (link)
Klein develops an argument against foundationalism along similar lines, although he departs from Sellars and BonJour in proposing infinitism rather than coherentism as an alternative to foundationalism. He imagines a proponent of foundationalism, Fred, who engages in a process of critical reflection on his justification for a certain belief. He traces back the chain of inferential justifications for this belief until he reaches some foundational belief that he takes to be nonI inferentially justified. Fred is committed, on pain of arbitrariness, to acknowledging that there is some feature F in virtue of which the belief in question is non-inferentially justified. But then the question arises whether beliefs that have F are likely to be true. And now there seem to be two options. If Fred ducks the question, or answers it in the negative, then his belief is epistemically irresponsible and so unjustified. But if he answers in the affirmative, then Klein (2007: 15) concludes, “the regress has continued because Fred has located a very good reason for thinking that b is true, namely, b has F and propositions with F are likely to be true.” (link)
If a certain belief can be self-justifying, however - and how we defend or attack a claim to one as such is a separate issue altogether - then a belief whose truth is its own justification is already all one needs to answer these questions. The belief itself is sufficient. These objections, like the objection to foundationalism Jeremy Fantl makes which I address in the above link, fail to address the foundationalist who states that foundational beliefs are self-justifying and, if of an internalist variety, infallibly so. To recall Fantl's admission:
We can ask why self-justifying reasons are self-justifying. If the traditional foundationalist has an answer, it seems like it must involve some metajustificatory feature. If the traditional foundationalist has no answer, it seems like the view has arbitrary foundations. (See BonJour, Structure, 30-3, for a similar argument.)
However, the traditional foundationalist can argue that completely self-justifying reasons are not self-justifying in virtue of some metajustificatory feature, nor are they arbitrary. It may be that certain reasons have to be assumed to be self-justifying if skepticism is to be avoided. This is a rather familiar form of rationalist argument for the existence of a priori justification. Here, the main implication of these arguments is that there might be a way to non arbitrarily show that we need to take certain reasons to be completely self-justifying without requiring that there be a metajustificatory feature which makes those reasons self-justifying. What convinces us we need to take those reasons to be self-justifying need not make them self-justifying.
This move does not seem to be available in the case of reasons that are self-justifying only to a degree. (pg. 544)
While "test[s] for truth" can serve as confirmatory evidences of Christianity, they shouldn't function as the ground of knowledge; divine revelation does. Elsewhere, I have called tests for truth necessary conditions for knowledge and the postulate[s] by which one claims to know anything the sufficient condition[s] for knowledge (link). The former are the means by which we make arguments for (i.e. apologetics) the latter (i.e. epistemology).
Again, apologetics should include an explanation of the epistemology of the system one is defending. Any good defense of a system of knowledge should explain what that system says about how we can know anything. But that explanation and defense should not be confused for that actual process of knowing. In fact, apologetics is only possible insofar as we know the system we are defending is true in the first place (see here).