Semantics Club 29 06 2001
Three papers appeared in the proceedings of LICS99 suggesting to change the usual underlying set theory for a non-standard one in order to deal with syntax involving variable binding. In this talk I will highlight the categorical structure which I think underlies some of this work. Moreover, I will try to explain Gabbay and Pitts' notion of \new-quantifier in such a way that the connection with the categorical structure mentioned above is made clear.