Chris Pratt has revealed that seeing his son "fight for his life" led him to devote his life to God

The Guardians of the Galaxy star - who has just been to Rome, where he filmed a documentary on St. Peter, and met Pope Leo - wrote in a personal essay for 70-year-old journalist Maria Shriver's The Sunday Paper: "I was baptised in a Catholic Church and have believed in God since childhood.

"I attended various religious institutions, including Catholic, Lutheran, and Evangelical churches. I knew little about the distinctions between denominations, but so much about the healing power of Grace.

"Mine was a broken road marked by cycles of sin and forgiveness; a pattern of rebellion, shame and grace on repeat, leading to increased extremes of emotional highs and lows.

"Then, when my son Jack was fighting for his life, I found myself back on my knees, pleading to God for a miracle. I promised that if Jack survived, I would devote my life to sharing God's message. This time I meant it."

Jack is now "healthy", and Chris - who is also dad to daughters Lyla, five, and Eloise, three, and son Ford, 13 months, with his 36-year-old spouse, author Katherine Schwarzenegger - thanks God every day for saving his eldest son's life, as well as for the existence of his other children.

The star - who described the trip to Rome as a "profound experience", which allowed him to delve deeper into exploring his faith - added: "I know how fortunate I am.

"I know there are countless parents who pray those same prayers and don't receive the answer I did. My heart is with them always.

"Ever since that moment, I've been trying to understand how best to speak of my faith - especially knowing that not everyone shares it. But whenever I can, I feel compelled to talk about the light my faith has brought into my life."

Chris also wrote about light and darkness as a way to describe the struggles he sometimes has with his spirituality.

The Jurassic World actor explained: "Darkness is not a presence. Darkness is simply the absence of light.

"Naturally, I want to share that light. But I struggle with how to speak publicly about my faith, knowing that brighter light casts darker shadows.

"I want to share the beauty of the light that changed my life. But the louder I shine, the more sharply some people see their own shadows - and instead of turning, they recoil."