In Fahrenheit 451 Faber states, "I talk the meaning of things. I sit here and know I'm alive." What does he mean?

Faber has a couple really great statements here, that show
the stark difference between a society that is filled with people that think and
analyze, verses a society that does not think, and merely lets others entertain them. 
When he says that he talks the meaning of things, he does just that--instead of just
stating the obvious, "The sun is shining," he discusses the deep, "Why is the sun
shining?  How does that sunshine impact my world?  How does it make me feel?"  He gets
beyond simple acknowledgment to a more thorough understanding that enriches his life. 
Most people in his society never ask why--take Clarisse for an example.  She doesn't
just look at the dandelions, she picks them, enjoys them, plays games with them, and
makes them relate.  She asks questions, she ponders
things.

When Faber says that he knows he's alive, he is
referring to the deeper impact that learning more than the surface can have on people. 
A well-known quote from the philosopher Descartes says, "I think, therefore I am."  This
means that in order to be more than simple robots that see the world but never process
it or feel it, we have to be able to think about the world, and why it is the way it
is.  We have to be able to understand the emotional core of experiences, and to not
drown out life with entertainment, stimulation and useless facts.  If you are able to
take a statement like, "the sky is purple," and care enough to dispute it, find out why
it ISN'T, and fight to have the real truth revealed, that is what makes you alive.  You
tell a robot, or many of the people in Faber's society, that the sky is purple, they
think, "Okay.  Who really cares anyway," and then go back to watching their television. 
Thinking, analyzing, questioning and acting are what make us alive, not automatrons that
never feel or act of their own volition.

I hope that those
thoughts helped; good luck!