Great Sermon! I really appreciated this lecture. However, in reference to your comments regarding the Presupositional approach to apologetics:
1. My understanding of the agrument for scripture is framed in such a way, from the presupositional position, in order to avoid any appearance of "neutrality". That is, we presupose the inspiration of scripture when dealing with an unbeliever thereby avoiding the error of answering a fool according to his folly.
2. The Westminster Confession makes it clear that the truth and divinity of scripture can only be recieved by a mind made receptive by the Holy Spirit.
The unbeliever is not in a neutral or receptive condition to believe or accept the truths of scripture and will always, apart from the grace of God, reject whatever argument presented that contradicts his unbelieving worldview.
I belive this why presupositionalists, for the most part, discourage the use of traditional arguments.