If you're unwilling to earnestly, critically examine/scrutinize your beliefs, and discard them in failing that scrutiny or in light of new information, you are doomed to stagnate as a individual.
An important sentiment in these times of belligerent, entrenched ideologies imho.
When his voice cracks saying "alternately, you could step away, and stand your revolution down" His overt desperation trying to lead a zygon to water and get her to drink gets me every time.
Acting!
(of course it helps when the written dialog is transcendant)
I loved his regeneration speech about how to be.
Always try to be nice, but never fail to be kind!
Never eat pears!