Should and ought: The rise of individually oriented modality in American English

Using data drawn from twenty American plays written since 1889, this paper analyzes the usage of the weak obligation modals should and ought, which previous researchers (e.g. Coates, 1983; Leech, 1987; Palmer, 1987) have regarded as essentially synonymous. It is shown that there is a clear distinction between these words, with should expressing individual opinions and ought emphasizing a common opinion regarding the obligation in question. This use of obligation should does not occur in five plays written between 1889 and 1911, appearing for the first time in this database in a play written in 1926. The development of obligation should parallels other changes in the modal system which have taken place at the same time - as should has increased in frequency, so have the other individually-oriented modals got to and gonna, and as ought has declined in frequency, so have the other group-oriented modals must and will.