could vs might (for expressing the future possibility)

Question

Could vs might(for the future possibility)

I could go there.

I might go there.

I know that these two sentences talk about less possibility to go there.

but, I can’t know their slight difference.

When you want to tell future possibilities, how do you determine to use could or might?

-------------------------------and-------------------------------------------------------------

There is an example sentence. -> He asked me last night if you could/might be willing to talk to Margaret for him. I saw this sentence on other website.

On the website, the writer explained that 'could' could mean internal possibility and 'might' could mean external possibility.

Internal possibility indicates whether the person is shy, not fluent, or which is related to his ability.

External possibility indicates whether there are some obstacles like that the person has no time to meet Margaret.

How do you think about that?

Thanks :)

Answer 1

Your first examples,
I could go there.
That sentence could mean either that I might go there (that it is a possibility), or that I am able to go there. For example, "I could go there, but I won't." That means that I am able, but there is no possibility

I might go there.
That means simply that there is a possibility that I will go there.

Your second example,
if you could/might be willing to talk
The question is about someone's willingness. To me, that is entirely internal to the person being asked. To my ear, "if you might be willing to talk" is more idiomatic.