[Lily Bracegirdle]

I have a couple of theories:

1) As others have said, Faramir was a friend of Gandalf. Now, why should this make Denethor unhappy? Beacause Gandalf is also the friend of Aragorn, who, under the name of Thorongil, made a great name for himself in Gondor when Denethor was a youngster. Denethor's father, Ecthelion, may have actually preferred Thorongil to Denethor. Denethor eventually came to suspect that "Thorongil" was Isuldur's heir, who would supplant him as ruler of Gondor (with help from Gandalf). Around this time, Thorongil conveniently left Gondor.

Now, Denethor and Boromir both felt that they could do very well without the King ever coming back. Their family had taken good care of Gondor for years and years, so why shouldn't they remain rulers forever?

Denethor had something of a seige mentality from living so near Mordor, so in his book you were either "with him or against him." Denethor probably saw Faramir's close friendship with Gandalf as a betrayal. To put it simply, Denethor thought "If you like Gandalf, you're his ally, and therefore a Royalist. That means you'll give up Gondor to Aragorn and depose your own father, who has worked so hard to keep this kingdom together. Ungrateful, treasonous wretch!"

2) Denethor and Faramir were very much alike in their intellect and intuition, much more so than Denethor and Boromir. And like things repel each other. Also, I get the feeling Boromir would have done whatever Denethor wanted, while Faramir would have thought about it and challenged his father more before obeying.

Of course, Denethor actually loved Faramir very much, but that didn't keep the two of them from fighting and misunderstanding each other just like any other father and son.

What do you think?

-Lily