While people treat the two verb forms as interchangeable, there is good reason to follow the straightforward principles governing usage.
Might is right - but then again it may be wrong
Max Hastings, the second of five editors for whom I worked at The Daily Telegraph of London, had strong views on most matters. One was that any reader who took the trouble to write to the newspaper should receive the courtesy of a reply. For reporters up against deadlines, this could be a tedious chore. But Max, now Sir Max, was right. In fact, the workload was reduced by the sizeable proportion of what we used to call "green ink letters". These were not always written in green, but did share certain characteristics. They tended to be long and rambling, contain slightly off-the-wall (or worse) theories or rhetoric and have a lot of text underlined. But they bore no legible name and address and could be safely discarded without fear of repercussions; in their own way, they were the ancestors of junk e-mails, though they never solicited bank account details or offered huge cash prizes for unentered competitions.
Sometimes, the mailbag brought grievances, justified or not, about items that had appeared in our pages. Occasionally, there were nuggets of information leading to important or at least interesting stories being written. JD Tunnicliffe was in a class of his own. He would write detailed, well argued letters pointing out errors of spelling, grammar or usage. One senior executive was so impressed by a single sheet headed "A note on the use of may and might" that he pinned it to the noticeboard where, I think, it remained until the paper moved to new offices.
These days, people treat the two verb forms as interchangeable. One or two dictionaries I have seen give, if not encouragement, clear signals that the distinctions are no longer worth worrying about. Mr Tunnicliffe would be horrified by such developments, and I find myself on his side. Looking back at a copy of the note that I kept, I find no reason to ignore the straightforward principles he listed.
Mr Tunnicliffe starts by pointing out that may is the present tense, might the past tense. In the example he gives, John tells him, using the present tense, that he may go to a football game; in the past tense, he told him he might attend. Might could also have conditional significance, he adds, though the condition is often implied rather than stated. Mr Tunnicliffe approves the use of may in the same context but says the condition would then need to be expressed (eg "I may go to the game if my wife decides to visit her mother") to avoid leaving the statement open, or unconditional.
Conversely, "I might go" is incorrect if the statement is genuinely open. Mr Tunnicliffe considers this to be a common mistake and recommends, as a rough test, using may if it sounds right. I believe he may have been optimistic to think this would help those with a tendency to use English sloppily. He might have responded that they would not be reading his advice in the first place. "May have" and "might have" are said by Mr Tunnicliffe to require special care. Broadly, "might have" concerns something that could have happened but did not ("Napoleon might have avoided the battle of Waterloo).
Complications arise if the sentence contains a sequence of verb tenses. If this produces serious ambiguity, our mentor favours overruling the correct grammatical form. "Major Jones reported that he might have destroyed two enemy tanks" suggests that he had an opportunity to destroy them but did not take it; "may have" introduces the missing clarity. But have such guidelines had their day? Perhaps in a world full of busy people rattling off electronic messages and spending less time reading the printed word, we do not quite need as many JD Tunnicliffes as we can get. Forgive me for believing we still need a few.
Colin Randall is a contributing editor to The National and may be contacted at email@example.com