If I understand you right you are basically getting at the same thing here. The use of reason is a common agreed upon shared standered that is social in this sense, common sense realism is right on this point. Van Til never denied this, he only put it in perpective. You can make great use of common notions but not make common notions autonomous, they are true because they are thinking God's thoughts after Him. Yes but you have not arived at an ought statement, the question still remains why I ought to follow your suggestion. Remember this is not the skeptic question of prove ethics itself but only a conception of of ethics, this principle is key to understanding all of continental thinking in general, aspect and direction or historical development of an aspect scientifically. You are correct in that the unbeleive can and does reason without a correct theory of reason. You are also correct in saying that the unbeleiver is still warranted in making rational statments and criticisms, for instance if a materialist logically criticizes my argument I cannot avoid answering that criticism by appealing to their inability to give a theory of reason. Notice that the TC is not a logical dodge of criticism but a criticism of the opposing persons general beleifs or worldview. First of all in what way is my statement either true by itself or an unnecessary repetition of words, or a tautology? I repeated the words to illustrate my method of TA that is all. I will answer your question because I brought up the issue of reason but to be fair I brought up ethics as well and you have answered those questions. Reason as a word can be used to mean many different things, for our discussion we will stick to the meaning of this word as a normative standard of authority. If it is not normative than it cannot be authoritative. So here are two preconditions that must be met to make reason what it is as we experience it: normative reason and authoritative. Another precondition that arises in this discussion is the issue of uniformity, that is to say reason must be uniform across cultural bounds and history. We must all use or do the same thing in order for reason to have any meaning. So our most general preconditions are these: 1. normative reason 2. authority 3. uniformity It might be asked why such a TA is needed when we experience all three of these things already in the very use of reason? This argument is circular in nature and therefore fallacious. So since we cannot appeal to reason by itself to explain itself we need a theory that satisfies these three preconditions. I think the Christian worldview does all these nicely. In the Christian worldview, henceforth CW, reason is simply a tool that we use to fulfill our nature as the image bearers of God, so that we think God’s thoughts after Him in making sense out of creation. So we see that the second precondition is met because the authority of reason does not rest in itself but in the very being of God, who is the Creator. So the modernist’s dilemma is avoided because we don’t have to locate the authority of reason in itself but in the Creator, this avoids the rash but correct conclusions of the postmodernists regarding the modernist enterprise. But what about the other two preconditions? Well the third one is answered by the very nature of man in the CW. We are all uniformly created as the image bearers of God. We uniformly use the same tool of reason in our attempts to make sense out of the world around us. So the first is therefore answered as well because uniformity and authority guarantee normative reason. To go against reason is therefore to deny our very being. Now I didn’t give the propositions you asked for because you are stuck on this unfounded notion that a TA must be formed in a direct deductive type argument. Since I have not seen any reason to do so I don’t feel the need to do so. If I did than this argument could never be proven in that way because it would be impossible to do so. Also this is as specific as I can get because again this whole argument could fill a book out.