Reddit atheists sometimes will argue that truth can only come through science. That which is true equals that which has been observed/tested. Thus a priori arguments cannot produce truth. This is very convenient for them, as the only arguments for God's existence that hold any water happen to be a priori. But it is simply untrue that a priori arguments cannot provide truth statements. My example is mathematics. Things like complex numbers were never actually observed or tested in the real world, yet they have been quite useful in predicting and explaining the world around us. To quote wikipedia, "the mathematical structure of a physics theory often points the way to further advances in that theory and even to empirical predictions... this is not just a coincidence and therefore must reflect some larger and deeper truth about both mathematics and physics." http://en.wikipedia.org/wiki/Unreasonable_Effectiveness As a lover of both philosophy and religion, I wish r/debateanatheist and r/debatereligion were more civil and intellectual. sigh