I got into a little debate with a christian.
She is saying that we cant compare unicorns to god, because god is "esse ipsum subsistens" - the sheer act of being itself.
This is Aquinas's definition of God.
What the hell is a sheer act of being itself?
Aquinas' God is existence itself. Essential, necessary existence, not contingent existence.
Basically, God is defined as necessary, therefore God is necessary. His argument doesn't actually get much more sophisticated than that. I find it childish and one of the least interesting arguments. He might as well define God as "argument winner" and insist that he has won the argument.