But that isn't to say that I haven’t been tempted to disbelieve in God's existence on numerous occasions. For one thing, a lack of belief in God is comparatively easy, at least from a moral standpoint. For another, problems with belief in the Christian God (such as the potential contradiction between an all-knowing God and an all-powerful God who is good, yet creates people who go to Hell) have often raised themselves.
Whenever I am tempted to doubt, however, I always come back to one proof of God's existence: that of miracles. Miracles require a supernatural answer - and there is only one entity that can provide a supernatural answer for certain phenomena: God.
To be sure, some supposed miracles are explainable through natural causes. (A cynic could easily dismiss the Eucharistic miracle of Siena, for example, as a 200-year old fraud perpetrated by priests.) But then there are phenomena which cannot be disproved, such as the Eucharistic miracle of Lanciano. In the eighth century at the rite of Consecration, a piece of bread was transformed into fresh human flesh (from the heart muscle), and wine was transformed into five pellets of human blood (which all weigh the same, despite being of different sizes.) Scientific tests have been performed on this miracle, which have failed to provide an adequate naturalistic explanation for it.
And then there is the famous incident of the sun dancing at Fatima, predicted by three uneducated schoolchildren after an appearance from the Blessed Mother. Richard Dawkins, one of the supposed intellectual deans of the atheist movement, was reduced to gibbering idiocy when trying to explain away the famous miracle of Fatima:
“It may seem improbable that seventy thousand people could simultaneously be deluded, or could simultaneously collude in a mass lie. Or that history is mistaken in recording that seventy thousand people claimed to see the sun dance. Or that they all simultaneously saw a mirage (they had been persuaded to stare at the sun, which can’t have done much for their eyesight.) But any of those apparent probabilities is far more probable than the alternative: that the Earth was suddenly yanked sideways in its orbit, and the solar system destroyed, with nobody outside Fatima noticing."
This is a gross misrepresentation of what happened at Fatima - no Catholic believes that the solar system was destroyed by the miracle of Fatima. which was a localized phenomena. But it is telling that one of the luminaries of the atheist movement was reduced to arguing that belief in any natural explanation of the miracle, no matter how impossible, was more likely than the barest possibility of supernatural influence.