I don't think the differences in any of these alternative words are very important. The important thing to me, if the objective is to find an absolute truth, is to find something which no one can reasonably deny. That is, which no thinking person can honestly deny.
If a thinking person said "I doubt that thought happens", then I think that would be equivalent to the person saying I don't think I think. Or, I think that I don't think.* It just wouldn't be a credible claim.
So the truth is, as I see it, that there is thinking or thought going on, or occurring, or happening, in some or all of our minds. If it is only going on in some of them, or even if it is only going on in mine (and the rest of you are illusions), the claim is still true: thought happens.
You might doubt that thought happens in my mind, but I don't think you can doubt that it happens in yours.
I think you and I agree, Dick, that it is futile to try to pin down any absolute truth strictly by choosing and defining words of language. But I think that we can get enough tacit agreement among ourselves on what each of us holds as a concept of "thought" and "happening" so that we agree that "thought happens" regardless of the exact meaning of those words.
I am really glad you put me on to this forum. It makes me feel less guilty for owing you a letter for so long. It's good to keep in touch this way. I still plan to send you a proper letter one of these days, though.
*I woke up at about 3:30 this morning half dreaming of a comedy sketch. I had a heck of a time getting it out of my mind so I could go back to sleep. The sketch went something like this:
Lou: Hmmm! I think...Yes! I think I think! Hey Bud, I thought I think.
Bud: You thought you thought?
Lou: No. I thought I think.
Bud: Oh. I thought you thought you thought, but you thought you think. Right.
Lou: I think so. But why would you think I thought I thought when I thought I think?
Bud: Well, I think I thought you thought you thought I thought you think.
(It's kind of fun to think of the many variations and to think about what each of them means.)