 Obviously, this list of skeptical arguments could be extended by varying either (a) the skeptical hypothesis employed, or (b) the kind of cognitive success being challenged, or (c) the epistemological principles that link the hypothesis in (a) and the challenge in (b). Some of the resulting skeptical arguments are more plausible than others, and some are historically more prominent than others, but there isn’t space for a comprehensive survey. Here, we will review some of the more influential replies to BKCA, BJUA, BKDA, and BEPA.