TAG is the transcendental argument for the existence of God. It asks (among other things) “What are the preconditions of intelligibility?” In other words, in order for you to have knowledge, what must be true? Here we need to clarify that last clause. Is the presuppositionalist asking, “In order for you to have knowledge, what must you account for to be true”? This would make the argument thus: how can your worldview account for logic, science, and morality?
Knowledge as Justified, True Belief.
Without using all the religious-ese in the statement, it is another way of stating knowledge as “justified, true belief.” This means that knowledge is I believe something to be true and am justified in that belief. In other words, I have to give internalist (intellectualist) accounts for knowledge. Greg Bahnsen clearly holds to this position. He writes, “To put it traditionally, knowledge is justified, true belief” (Bahnsen 178). He glosses justification as “sounds reasons (good evidence” for a belief. At this point Bahnsen is in line with the traditional models of epistemology.
It seems, moreover, that the TAG-ist is asking the skeptic (or whomever; TAG works better on skeptics than it does on adherents of other theistic systems) to account for justifications (or preconditions) within his own worldview. Bahnsen writes, “The Christian claim...is justified because the knowledge of God is the context and prerequesite for knowing anything else whatsoever. Furthermore, the unbeliever is asked to account for any “theoretical sense” of “any kind on the subject” (262). It is here I suggest that Van Tillian presuppositionalism--at least in the extreme TAG variety--is a form of internalism.
Justification seeks the satisfaction of epistemic duty. Applied to the Van Tillian case, the person must fulfill an epistemic duty in order to have true knowledge; namely, the duty is to “establish the preconditions of intelligibility.” Further, since it involves the formation of a belief, it is internal (hence, internalism). Internalism also involves a view of cognitive accessibility (Plantinga 36), but this isn’t relevant to the above discussion.
The Gettier Problem
Edmund Gettier suggested a number of scenarios that show where someone can know something yet not really have justification. A fourth criterion is needed. For example, I look at a field in the early morning fog and see what I think is a sheep. As it happens, it wasn’t a sheep but a wolf in sheep’s clothing. Unbeknownst to me, there was indeed a sheep in the field behind the wolf. Technically, I was correct. I saw something in the field that I thought was a sheep. It was true belief and I was justified in holding it, yet it wasn’t knowledge (Plantinga 32). While this may not be the most powerful Gettier problem, the reader can consult here for more examples.
Externalism, by contrast, notes that many people have knowledge of situations s...z without being able to give ultimate justifications for their knowledge. They would say, rather, with Thomas Reid and Alvin Plantinga, “ Any well formed human being who is in an epistemically congenial environment and whose intellectual faculties are in good working order will typically take for granted at least three things: that she has existed for some time, that she has had many thoughts and feelings, and that she is not a thought or feeling” (Plantinga 50).
This paper does not try to show whether TAG is in fact false (I think it is). Rather, that it rests upon improper foundations. Furthermore, the challenge given by hard presuppositonalists (e.g., can you account for the preconditions of intelligibility? OR such-and-such thinker is in error because he did not challenge the unbeliever’s foundation) is itself a non-starter. This paper, in conclusion, merely stated the view of externalism and did not seek to prove it to be true or false, as it is not used by TAG presuppositionalists.
Bahnsen, Greg. Van Til’s Apologetic: Readings & Analysis
Plantinga, Alvin. Warrant and Proper Function.