May and Might

Hi,

I think the modals 'may' and 'might' are used in part to indicate a different spectrum of time frames, one to indicate the past of the other. But I feel it may not be that simple and obvious for cases like these. I feel the cases illustrated here demonstrate that they can be used in place of each other with no seemingly real differences:

In the future, I may/might do this to improve myself.

Three days ago, I may/might have thought this was the right thing to do.

I may/might not do this right now.        

I may go now.  I have permission to go now vs. It's possible that I'll go now. 

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may not is even more likely to be ambiguous in the same situations.  (This one is so ambiguous to my ear that I never use it.)

I may not go now.  I don't have permission to go now.  vs. It's possible that I won't go now. 

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may have and may not have are not ambiguous in this way, as permission isn't given for past actions.

He may have left.  It's possible that he left.  [No alternative involving permission.]

I may not have understood.  It's possible that I did not understand.  [No alternative involving permission.]

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might, might not, might have, and might not have are ambiguous only in subordinate clauses, as in reports.

I might go; I might not go; I might have gone; I might not have gone.  [All involve possibility, not permission.] 

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All of the permission uses of might shown below are less used in modern English, especially the negatives, but you may encounter them on occasion. 

He said I might go.  He said that I had his permission to go.  vs. He reported the possibility that I would go.

He said I might not go.  He said that I did not have his permission to go. (not as likely in modern English)  vs. He reported the possibility that I would not go. 

He said I might have gone.  He said that I would have had his permission to go.  vs.  He reported the possibility that I had gone. (most likely interpretation)  vs.  He gave his opinion that I should have gone (as a mild reprimand), although I didn't.  This last is nearly equivalent to He said it wouldn't have hurt me to go. (more used than its negative companion below)

He said I might not have gone.  He said that I would not have had his permission to go. (not as likely in modern English) vs.  He reported the possibility that I had not gone. (most likely interpretation)  vs.  He gave his opinion I should not have gone (as a mild reprimand), although I did.  This last is nearly equivalent to He said it wouldn't have hurt me to stay away.

CJ 

Hi,

What I can come up with is this:

It might be the case back then, but now, this is how it works.

As to CJ's explanation, I might have to take a long look and learn from it.

I just saw the following caption for a photo on Yahoo News: 

"Some think this strobelight gun may have helped the U.S. win WWII sooner."  [emphasis added]

When I read this, I assumed that the strobelight gun was actually used, and that the meaning was "Some people think it is possible that this strobelight gun actually did help the U.S. win WWII sooner than they would have if they had not used it." But when I read the complete article, I discovered that the strobelight gun was never used, and the real meaning of that caption was "Some people think it is possible that this strobelight gun, if it had been used, would have helped the U.S. win WWII sooner than they actually did." My feeling is that a more correct caption would be

"Some think this strobelight gun might have helped the U.S. win WWII sooner."

 It seems to me that "may have" always suggests the possibility that something actually happened. "Might have" can mean the same thing as "may have," but it can also suggest the possibility that something would have happened given some counterfactual condition: "might have X, if Y had been the case."

Or maybe this is just my personal feeling. Does anyone have a different opinion?

I'm with you.