There is a sense in which each event in our life is new and unique, just as each sentence in our language is one of an infinite variety of possible sentences. Yet there is also another quite different sense in which both events and sentences are recurrences – reiterations, replays, reminders – of earlier instantiations of life and language. Not only can we speak of déjà vu experiences when we feel that we are reliving something that has happened before, for example, but our days are often organized by routines and schedules; we follow scripts; we learn how do things by repeating them. And although our sentences may be filled with different words, and their constituents differently arranged and combined, they all follow the implicit rules of our grammar.

These two perspectives on ‘same’ and ‘different’ bring to mind something that my husband Louis once casually mentioned to me several years ago as a way to characterize people. Although Louis cannot now remember where he heard (or read) it – just as I cannot remember exactly when, how, where or why he mentioned it to me – we both remember the gist of what he said. It was this: the world can be divided into two kinds of people, either lumpers (who focus on similarities) or splitters (who focus on differences). Louis could firmly characterize himself as a splitter, in both his everyday life and his work.