  Note that the parentheses in Leśniewski’s notation do not themselves have a category: they are syncategorematic. Their function is twofold: to mark the beginnings and ends of argument strings, and to help indicate the semantic category of the functors. Thus Leśniewski used round parentheses for functors yielding sentences from sentences, i.e. connectives, and braces for functors yielding sentences from names, i.e. predicates. In principle an unlimited number of shapes of parentheses might be required, and indeed in some works of students of Sobociński there are several dozens of different shapes. Leśniewski gave parentheses this second role because he wished to remain very flexible about the forms of expression used for functors, even allowing the same shape to be used in “analogous” functors, for example 3-placed conjunction, or “higher-order” epsilons and equivalences, or other logical constants. Obviously this is a contingent feature of his notation: other conventions will do just as well.