The Return of the Flashback

[Boromir88]

In addition to those five, there's also Arwen's vision of Eldarion.

Plus the ROTK EE where Denethor sees a "Ghostly apparition" of Boromir appear. I love this because I think it just goes to further show Denethor's loss of control over his mind. He's stuck in the past, caught up in all this despair that's gone all around him, he can't get "passed the past."

I had a wonderful conversation with Lalwende over Denethor here. In which case I think we do get a sense that Denethor was once a much better man than he was later on. However, he is got up in the past, with the loss of his wife, the loss of his son and heir and he can't get passed the despair like Theoden was able to. I think this little flashback of Denethor's in the movies goes to show this perfectly.

This may not be a "true" flashback where we get a look at the past, but for Denethor it is a flashback, remembering his lost son and thinking he's there.