Tim Keller says he lived "in denial" about death and only "half-believed in the resurrection" until cancer forced him to re-examine his faith.

The bestselling author and pastor was diagnosed with cancer for the second time last year. The prognosis wasn't good as it was stage four pancreatic cancer with a life expectancy of no more than a year from diagnosis. 

Keller reveals in an interview that the diagnosis was a wake-up call that made him look afresh at what he really believes. 

"When you know you could die very, very soon, you realize that you basically live in denial of the fact of your death," he said. 

"When it suddenly strikes you, you have to ask, 'Do I have the faith for this? Do I believe that the resurrection of Jesus Christ really happened and that if I die in faith in Jesus, I will know that resurrection too?'"

The 70-year-old said his condition is "very serious" but the chemotherapy has been going well and he's hopeful that he's got "years and not months left" to live.

"My wife Kathy and I are pretty grateful; it looks like I've got more time than we thought when we originally got the diagnosis," he said.

But he hasn't been resting on his laurels. Over the last year, "The Meaning of Marriage" author has been busy doing both "intellectual and emotional work", and he published his latest book, "Hope in Times of Fear: The Resurrection and the Meaning of Easter" last month.

Discovering he had cancer had a profound impact on his faith - and his new book. 

"Here I am, writing a book about the resurrection, and I realized I only half-believed I was going to die," he recalled.

"I went back and realized that in some ways, I also only half-believed in the resurrection — not intellectually so much, but all the way down deep in my heart.

"I realized I needed to have a greater, a deeper faith in the resurrection, both intellectually and mentally." 

While he did the necessary historical research for the book, he also spent a lot of time in prayer and Bible reading to rediscover the truth of the resurrection for himself. 

"It took several months in which I had to take my abstract belief down into my heart to existentially and experientially know it and grow in assurance, and it worked," he said to CP.

"If you are willing to embrace the truth of God's Word and immerse yourself in it day in and day out, and then ask the Holy Spirit to make it real to your heart, He will."