The distinction I was trying to make was this: let's assume we're voting on a piece of proposed legislation (say, Medicare, in the 70s.) My fundamental Christian beliefs guide my vote, in the sense that I believe that we have an obligation to love one another; I decide to vote yes. But, when I propose an amendment that says that Medicare benefits are only available to those of my own denomination, because I believe mine is the true faith, I have crossed the line between separation of church and state.

The current debate over abortion is actually a manifestation of proper influence of personal belief without imposing a state religion. (For what it's worth, I'm pro-choice.) Those saying that the federal government should not fund abortion are informed by their own beliefs (at least their morals, perhaps also their religion); so are those who argue that the government should fund it. However, were they to say that only the Methodist church could determine who should and shouldn't be allowed access to abortion - the line is crossed.

I don't know if that helps or not. I was merely trying to say that all of us are influenced by our moral/religious beliefs in our decisions (from whether or not to attend church, to what charity we contribute to, to the ethical decisions we make in business) - but when we try to use political power to favor one religious group over another, we've crossed the Constitutional line.

Or, maybe: we can each follow our own moral compass; but I can't force you to use mine - and vice versa.