I'm sure you've encountered all manner of theories purporting to explain the significance of things coming in threes. Here is another one for your collection, from 'Discourse & Conversation Analysis', an interesting branch of sociology that concerns itself with the linguistic and behavioural conventions that underpin day-to-day social life.
In the words of Potter, (1996: 196), it is very common for lists to be delivered with three parts or items.
Some idiomatic examples are:
- "here, there and everywhere",
- "Tom, Dick and Harry",
- "single, white and female".
Some three-part lists end with 'generalized list completers' such as "etcetera" or "that kind of thing".
Conversation analyst Jefferson (1990) has noticed that three-part lists are frequently used to summarize some general class of things.
Three parts are enough to indicate that we have more than individual instances on their own but instances standing for something more general (Potter, ibid.).
For instance, my list of specific examples of lists in the last paragraph indicates the class of lists in general.
Three-part listing is a linguistic resource that has a range of functions in everyday social interaction. For instance, three-part lists are conventionally treated as strengthening or affirming a broader, overarching position or argument (Hutchby & Wooffitt, 1998).
The three-part list is, among other things, a persuasive rhetorical device.
Hutchby, I.& Wooffitt, R. (1998) Conversation Analysis. Oxford, UK:
Blackwell Jefferson, G. (1990) 'List construction as a task and resource', in G. Psathas (ed.), Interaction Competence. Lanham, MD: University Press of America
Potter, J. (1996) Representing Reality: Discourse, Rhetoric and Social Construction. London: Sage
Contribution from Rachel