The mishna has an inner contradiction about whether or not a general oath would include eating not kosher foods. Two different resolutions are brought. What are the reasons why one would say that an issur kollel would apply or not? Rava says that applies even in a case of one who swears. The gemara brings a mishna in kreitut which would seem to contradict Rava and 6 different explanations are brought as to why there is no contradiction.