[Boromir88]

Phantom, you bring up some good points.

I'm not sure I agree that his desire was "irrational".

This is irrational-> expecting a hobbit to safely enter a heavily guarded land, travel for miles and miles without getting caught, and destroy a ring he could not willingly throw into his little fire at home.

Boromir's plan is irrational, but you are right that it's definately rational compared to the other plan, which is practically like suicide.

I agree with the first part and the last part, but I do not agree that he was "mentally, the weakest".

Possibly, he may not be the "weakest mentally." As we see Aragorn take on the role of Gandalf, he too becomes "mentally weak." When the proper chapters come, I will point out the quotes. But, these last closing chapters, he begins to doubt himself, and get down on himself for the decisions he made. Basically he blames himself for the whole problem that occurred (capturing of Merry and Pippin, death of Boromir, running off of Frodo), he goes through this tough period where he doubts himself.

Why? Because I'm weaker mentally? No. Because I'm strong- and I would believe that, despite the warning, my strength would be enough to do it. My cousin, on the other hand, is not used to doing things the way he pleases but used to following his elders and so would trust and obey the judgment of his elders.

Do you understand what I mean?

That makes sense, I think we can see that in Boromir's word's at the council of Elrond.

"I do not understand all this," he (Boromir) said. "Saruman is a traitor, but did he not have a glimpse of wisdom? Why do you speak ever of hiding and destroying? Why should we not think that the Great Ring has come into our hands to serve us in the very hour of our need? Wielding it the Free Lords of the Free may surely defeat the Enemy. That is what he most fears, I deem.
"The men of Gondor are valiant, and they will never submit, but they may be beaten down. Valour needs first strength, and then a weapon. Let the Ring be your weapon, if it has such power as you say. Take it forth and go forth to victory!"

You are right, I think Boromir doesn't believe it would be able to corrupt such a man as he, or one of these "free lords." He speaks of. A situation we can connect to this would be Denethor and the Palantir. Denethor didn't "view" the palantir because he was "mentally weak." He viewed it because he thought he had the strength to combat Sauron, now obviously he doesn't have the power of Sauron, so in time his "mind broke" because he lost the "battle" with Sauron, but it wasn't because he was mentally weak, nice point. I would go in further, but I'm afraid Esty will repremmand me, so maybe I can make it a thread of my own.