Whenever I read philosophy throughout history regarding God, I notice something I have issue with: Philosophers in most cases define god to be omnipotent, omniscient, and omni-benevolent.
The first two conditions are obvious: I can see where being all-powerful and all-knowing would be necessary conditions for a God.
But why is it necessary that God be omni-benevolent? Of course the Christian god must be omni-benevolent, but then why do philosophers almost exclusively focus on the Christian god?
For instance, the problem of evil is that it seems like omni-benevolence, omniscience, and omnipotence are incompatible with evil in the world. But again, why are we assuming God to be all good? A very simple solution to me is that: There may be a God, but he may not be good. Do philosophers ever argue that position?
So I guess my question is:
Why, from my admittedly limited exposure to western philosopher, to we place such prominence on arguing for the Christian god's existence or non-existence?
Where did the idea that if there is a god, then it must be good come from, aside from the Bible?