[Doctor Stochastic]

One main argument for a heliocentric system is that one can have the law "things further out move slower than those closer in." This law fails in a geocentric system.

[PatrickHenry]

One main argument for a heliocentric system is that one can have the law "things further out move slower than those closer in." This law fails in a geocentric system.

I may be wrong, but this is rather like my understanding of the parallax argument someone raised earlier -- "If earth's orbit didn't have this particular diameter, then that star wouldn't be x lightyears away."

Yes, everything we've figured out after we had a solar system theory is consistent with the solar system, but I don't know if that proves the solar system. I guess what I'm struggling to say is that we can start with observed data and reach great conclusions, but does the reasoning work backwards? Do the conclusions somehow validate the original observations?

I know my limitations, and I shouldn't argue an issue like this with you, as you're quite likely to blow me away with something of which I'm unaware.

[PatrickHenry]

Upon reflection, your argument is a good one, but only if you recast it in this form:

If and only if p, then q.
And we have q;
Therefore p.

Otherwise, it would be a classic fallacy: "If p then q; and q; therefore p."

So your point may be spot on, depending ...