Difference between could have and might have

Im with stupid ->   Monday, October 04, 2004, 04:41 GMT
I have a tough one here, I was faced with a tough question. What would you have done if you hadn't become a model? I could have become a zoologist.
Is it possible to use might have become a zoologist. I was thinking could have just has more possibility than might have. Please explain
Jim   Monday, October 04, 2004, 04:57 GMT
I think it's a question of desire.

Suppose it had been possible for you to have become a zoologist and suppose that you would have liked that. Use either.

Suppose it had been possible for you to have become a zoologist and suppose that you would not have liked that. Only use "could have" not "might have".

Suppose it had not been possible for you to have become a zoologist. Use neither.
Mxsmanic   Monday, October 04, 2004, 07:02 GMT
Could have = it was possible
Might have = it was permitted

Remember, could is the past tense of can, and might is the past tense of may. Can expresses things that are possible in an objective sense; may expresses things that are permitted or can readily be envisaged (this usually implies that they are objectively possible as well).

What will you do if you don't become a model? I can become a zoologist. I know that because I have good grades.

What will you do if you don't become a model? I may become a zoologist. I don't know if it will interest me, though.

Using present and future tenses instead of past tenses makes the statements much more definite, much less hypothetical. Hypotheticals are usually expressed with past tenses (would, should, could, might).
Jim   Monday, October 04, 2004, 07:08 GMT
Mxsmanic's right. "Might have" can mean "it was permitted". But I wouldn't say "I may become a zoologist." if I didn't want to become one.