Sorensen on Begging the Question
Sorensen's argument is valid. Moreover, premisses (1), (2), and (3) seem uncontroverisal. (I will show that premiss (3) is dubious later.) And premiss (4) can be derived from premisses (2) and (3), plus a certain inferential characteristic of argument (A), as can be shown as follows. If you agree with the premiss of (A), you agree with its conclusion. So, according to premiss (2), (A) does not beg the question against you. On the other hand, if you do not agree with its premiss, then you have to say that there is no fallacy of begging the question. Since you hold that there is no fallacy of begging the question, you cannot consistently condemn argument (A) as begging the question against you. So, according to premiss (3), (A) does not beg the question against you. Therefore, the conclusion that (A) does not beg the question seems inevitable. Therefore, Sorensen concludes, assuming what you are to prove does not imply that your argument begs the question (see also Sorensen 1991).