Is everything relative?

One of the great philosophical/existential questions of all time is "If a man is standing in a forest all alone and screams, with absolutely no-one around, did he really scream?

But don't get confused, this is not the same as a married man asking "If a man is all alone in a forest, is he still wrong?" back to the point ...

Relativism. It's a bitch. It's all around us. It calls everything we believe into question. How can we REALLY know that God exists? How do we REALLY know when God is speaking to us?

A bit of history - the relativism argument has not been around all that long. In what is known as the modern (1500 - 1900) and pre-modern (pre-1500) periods science and the church ruled as authorities on truth.
The pre-modern argument when the church ruled was that God was God and there was not alternative Truth. In the modern times when science ruled, scientific reason was the authority as proven through scientific enquiry.

Now, in our post-modern times, reason and our free-thinking is the authority (also known as humanism). I've struggled with relativism most of my post-teen thinking life, and have now learnt not to give it too much room, but to rather learn what faith means in the face of very good arguments against the Truth I follow (Jesus).

This is my take on things, what is yours? (Sheesh, now wasn't that a relativist question?)