So today my friend and I were discussing whether or not a certain part of the movie Back to the Future III was actually a plot-hole.

The event in question is when Marty shows Doc the letter at the beginning of the movie. Doc then knows that he is eventually going to be in the old west working as a blacksmith. Doc and Marty later find out that Doc is going to be murdered in the old west. Doc sends Marty to the past in an attempt to warn future doc who is in the past.

This is a plot-hole. The Doc who is in the old west should already know that he is going to be murdered, considering that he is the Doc of the future (I think we can assume that his memory isn't that bad.)

Of course, all of this is assuming that we completely bypass the fact one cannot travel through time or effectively make a time travel movie, being that if someone correctly traveled back in time to change something, there wouldn't actually be any reason to (if you don't get this now, think hard about it for a strong feeling of mental satisfaction).
We should also forget about the whole "fading words on gravestone picture" thing.
Why would there be nothing written on the tombstone of a an empty grave?

Anyway, the whole conversation is now settled and it has been determined that I was right XD.

Here is a diagram to explain it to any of you who are confused: