The Formal Presuppositional Argument?

I noticed that Dusman, an administrator over at Gene Cook's forum formalized the Presuppositional argument* in the thread about John Loftus’ appearance on the Atheist Hour:

1) For X to be the case, Y has to be the case.
2) X is the case.
3) Therefore, Y is the case.

Read that first premise to yourself slowly a few times. Does that seem strange to anyone? This is not the standard language used to make a conditional statement. The standard language would be:

"If X is the case, then Y is the case."

But why isn’t the presuppositional argument stated clearly as an if-then conditional? Why is it stated as a for-has? This presuppositional phrasing is awkward- making it difficult to determine which is the antecedent and which is the consequent. But is the meaning of the statement changed if the statement changed directly to an if-then conditional, as shown above? This translation doesn’t seem to be completely accurate- in the presuppositional for-has conditional, the truth of X is dependent on the truth of Y. But in the if-then condition, the truth of Y is dependent on the truth of X. These statements are not equivalent, so clearly it’s not accurate to translate the presuppositional for-has conditional directly into an if-then.

But what if X and Y were flipped? In this event, the conditional would read:

“If Y is the case, then X is the case.”

Here we see that the truth of X is dependent on the truth of Y, just as in the presuppositional for-has conditional. So, the two wordings of the statement are equivalent, and we are now able to use a much clearer if-then conditional to reexamine the presuppositional argument:

1) If Y is the case, then X is the case.
2) X is the case.
3) Therefore, Y is the case.

Now we can easily see that this argument takes the form of the logical fallacy Affirming the Consequent. It makes sense why Dusman needed to use the for-has phrasing that he did to hide this fallacy- although grammatically confusing, the presuppositional use of for-has results in listing the consequent prior to the antecedent in the conditional statement, giving the illusion of a perfectly valid modus ponens.

But why would the presuppositionalist risk a logical fallacy just to make his argument? Why not simply construct a valid modus ponens and stand by it? My guess is that he then runs the risk of being accused of a more informal non sequitur, as many explanations can be given for X being the case without calling upon Y. But since the truth of X is uncontested by all, and in fact presupposed by any who would seek to argue logically, the presuppositionalist tries to use this acceptance of X as a wedge to force acceptance of Y, by making the truth of X dependent on the truth of Y. Unfortunately, this is a fallacious argument as I’ve already noted.

I’m inclined to suppose that this underlying error may be the reason why the presuppositional argument is so rarely displayed formally- I’m frankly surprised that Dusman did so without provocation, although he was in the comfortable setting of a presuppositionalist forum. This was the first time that I’ve seen the for-has phrasing of the major premise- on the one occasion that Paul Manata formalized the same argument, he used a slightly different strategy:

1) If X is the case, then Y is the case (since Y is the precondition for X)
2) X is the case.
3) Therefore, Y is the case.

I’m sure that by this point, you don’t need my help to see that this is committing the same error. By inserting additional information about the relationship between X and Y parenthetically, Paul has made the truth of X dependent on the truth of Y, and thus enters into the same fallacy as Dusman above.

Of course, this is just based on the postings of two individuals who claim presuppositional apologetic strategies. They may be incorrect in their formulation of the presuppositional argument, in which case I look forward to seeing the real McCoy. Or maybe there are some subtleties to the argument that I’ve missed. Either way, I’m eagerly anticipating edification.

* in the presuppositional argument, X=logic and Y=God