If an atheist exists, then God must also exist. To understand this maddening and confusing statement we must first examine whether God exists. If he exists then we can breathe a sigh of relief and conclude that atheists also exist.
Does that make no sense at all to you? Don’t worry, it’ll make even less sense soon. I’m shortening the argument somewhat for convenience.
Whether God exists or not depends on whether anything exists. The question is not whether God exists, but the more fundamental question of “why is there anything at all?” We see that there are things that exist. There are trees and animals and human beings and rock and plants and there are atheists too. But do they really exist? Yes and no. They are here now, but they will not be here forever. All the things we see (including the atheists) are mutable. They change.
In the long view, all the things that exist around us are ephemeral. They will eventually cease to exist. They will be no more. They will be dust. They will be deceased. Since they will one day be dust, how can we say that they really do exist at all?
If they exist — even for a time — then there must be some other quality to their existence that enables them to exist. Something must be holding them up.