But... (and that's
a really BIG but)
but beginning a sentence.
“In his youth Dostoevsky had been attracted to utopian socialism of the Fourierist variety. But four years in a prison camp in Siberia shook his faith.”As this quotation from J.M. Coetzee shows, the conjunction but can be highly effective as a sentence opener. You may still hear the injunction against beginning a sentence with a conjunction. The idea is that these sentences express “incomplete” thoughts. But a glance through any magazine or newspaper will show you that beginning with but has become common practice, and initial but must be considered acceptable at all levels of style.
but not followed by a comma. But is generally not followed by a comma. Correct written style requires:
Kim wanted to go, but we stayed.not
Kim wanted to go, but, we stayed.