  The Fregean revolution in our conception of  logical form  made this way of demarcating the logical constants problematic. Whereas the term logicians had seen every proposition as composed of subject and predicate terms linked together by syncategorematic “glue,” Frege taught us to see sentences and propositions as built up recursively by functional application and functional abstraction (for a good account, see Dummett 1981, ch. 2). To see the difference between the two approaches, consider the sentence