In a recent debate on science and religion, Professor McGrath said that atheism was "hopelessly simplistic", while Christianity offered a more compelling framework within which to explore science.
"I felt [atheism] was hopelessly simplistic, or at least the forms I knew. And I think what really drew me to Christianity was this deep sense that it offered me a bigger picture of things," he said.
"A way of making sense of myself, of our world, and also providing conceptual space for science. In other words, I continued to love science as something that really mattered, but having a framework into which I could fit it."
Professor McGrath was debating US biologist Bret Weinstein, one of the leading voices in the 'intellectual dark web' who does not believe in the existence of a supernatural deity.
Weinstein was professor of biology at Evergreen State College in Washington until 2017 when he was forced to stand down after criticising a 'Day of Absence' that suggested white students and staff should stay at home.
While he doesn't believe in a deity, Weinstein acknowledged that God was a "hack" that people needed to learn right from wrong.
"In Catholicism, the fact that you do wrong and that wrong counts against you in a way that you can relieve yourself of the debt but you have to confess it to somebody who is then in a position to give guidance to you," he said.
"Again, it's a hack. It correctly teaches you that this is wrong through some mechanism that has to be instantiated in the real world and it can be done through metaphor."
He admitted he couldn't think of anything that could be as effective at instilling this kind of moral compass in people.
"Can you, if you are aware that there is nobody up there actually watching, write a code that is equally effective at getting people not to behave in this way? That's going to be tough," he said.
"On the other hand, I'm not sure we have a choice ... It must be done now through insight and enlightenment and that's not going to be easy."
Professor McGrath argued that Christianity did not merely serve as a "useful function" in society but that it was the existence of God that gave sense to concepts of right and wrong.
"I think that one of the significant things about believing in a righteous God is this deep sense that when society goes very badly wrong there is something against which we are being judged," he said.
"And if you look at, for example, Germany during the late 1930s you see a resurgence of the kind of approach you and I would probably call 'natural law'. In other words, the law is being rigged to, in effect, do all these things. There has to be somebody above this who's able to say, 'this is not right'.
"I think that there's a lot of reason to think that we as human beings are trying to see how we fit in to a bigger picture. If you articulate that in terms of God then, in effect, you are fitting into a bigger picture which actually gives you a sense of who you are. What the whole point of things is."
The debate was filmed in front of a live audience at the Institute of Mechanical Engineers in Westminster for the first episode of season 2 of The Big Conversation series by Premier Christian Radio's Unbelievable? show.