There’s a popular field of religious apologetics called “Presuppositional Apologetics” in which the religious apologist, rather than debating the evidence, compares and contrasts different worldviews to show that only the Christian worldview provides a foundation for the existence of knowledge. The claim is that only with God can you know that your thoughts and senses are reliable, and that the laws of nature won’t suddenly change tomorrow, etc.
So how does a Christian worldview claim to justify these ideas? Well these apologists claim to know, with absolute certainty, that God exists, and that God wouldn’t let such bad things happen. In fact, they even claim that atheists know that God exists, but they are “suppressing the truth in unrighteousness”.
This whole idea comes from Romans 1:18-20.
"18 The wrath of God is being revealed from heaven against all the godlessness and wickedness of people, who suppress the truth by their wickedness, 19 since what may be known about God is plain to them, because God has made it plain to them.20 For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse."
This is a core argument of presuppositional apologetics, and I will dispatch it now. I’d like to present one question I’ve asked presuppers, and then I’ll give my responses to their answers.
The question is: What do you mean when you say I, an atheist, “know” that God exists?
A. You consciously know that God exists, but you lie and say you don’t. Just like if you knew your phone bill was overdue, but you chose to ignore it.
B. You know it unconsciously: you know it deep down, but you don’t recognize that you know it.
And now for my responses to these two answers:
1A. Do you really think that atheists are that stupid? Do you think we’re sitting around thinking, “Man, I really want to watch porn and get drunk and hate God, but I don’t want to go to Hell for it… I know! I’ll pretend that God doesn’t exist! It’s the perfect solution!”
Actually, in this day and age, speculation about atheists’ inner thoughts is not necessary: we have lie detectors; you could hook me up and demonstrate that I’m not lying. But I doubt many apologists would accept this fact if it were presented to them.
1B. Not recognizing that I know something is the same as not knowing it. To see how this works, let’s look at an analogous claim:
My favorite color is green; I have green sheets, my bedroom walls are green, my carpet is green, and in general, I like green things. If someone comes up to me and says, “Well, you think your favorite color is green, but it’s actually orange, you just don’t realize it”, in what sense is this true? In what sense is my favorite color “actually” orange if I like green in the way I described above?
This is an example of the No-True-Scotsman fallacy: Person A presents a universal claim (“Everyone knows that God exists.”), person B presents a counter-example (“I don’t believe in God.”), and person A, rather than debunking the counter-example or admitting that their claim is wrong, superficially changes their claim to try and fit both ideas together (“Well you don’t 'truly' disbelieve.”). But again, what does it mean to disbelieve, but, at the same time, to not “truly” disbelieve? This is a meaningless assertion.
And with that, presuppositional apologetics has lost its flagship: despite what the Bible says, atheists do not, in any sense of the word, know that God exists. That’s why we call them “atheists”.