Having been under the impression that categorial grammars in general and the so-called syntactic calculus in particular had been swept away by the tide of transformational grammar, I was very surprised to learn of the recent revival of interest in these matters, as, for example, by Buszkowski in Poland and by van Benthem in the Netherlands. Stimulated by the renewed activity in this area, I decided to take another look at it, and in particular, to explore the categorical connection, which had been at the back of my mind all along.