Christian pastor and author Timothy Keller took some time earlier this week to do a question-and-answer session on Twitter, and gave several pearls of wisdom for dating, marriage, apologetics, and evangelism. Below is a brief summary of the Q-and-A.

It's no secret that Tim Keller has greatly enjoyed the writings of C.S. Lewis. The contemporary Christian author often uses allegory to help explain the richness of Christ more deeply himself, in fact; the use of story puts "theoretical truths in ways I can relate to them," Keller says. He cited "Mere Christianity" as his favorite C.S. Lewis book, and also said he enjoyed reading the Harry Potter series. "Great examples of sacrificial love conquering evil reminds me of another story," he quipped.

Keller, who is a gifted teacher and pastor of Redeemer Presbyterian Church in New York, marries the intellectual pursuit of Christ with worship. One participant asked the pastor what the main difference between teaching and preaching is; "The goal," Keller says - "The goal of teaching is inform the mind, maybe warm the heart, but preaching is worship."

The Gordon-Conwell Theological Seminary (M. Div.) and Westminster Theological Seminary (D. Min.) graduate advises seminarians to avoid a purely intellectual pursuit of Christ by asking practical questions along with their academic endeavors. "The 'so what' and 'why' questions mean there is a reason for your learning," Keller says.

The Christian pastor has written a New York Times best seller on apologetics entitled "The Reason for God: Belief in an Age of Skepticism." The main purpose of apologetics, Keller tweeted, is to clear the way for evangelism. One of the biggest challenges in modern evangelism, he believes, is the fact that Christians and secular America seem to have less and less common ground to stand on. He calls the world's all-too-common charge of Christian "narrowness" unfounded - in fact, if he could speak on only one apologetics topic to a college crowd, Keller says he'd "Show that there is no such thing as a non-religious view. All views are inherently religious."

The author of "The Meaning of Marriage: Facing the Complexities of Commitment with the Wisdom of God" has plenty of sound advice to give on dating and on marriage as well. One fan asked whether differences of opinion on a theological issue such as infant baptism should cause someone to rethink their dating relationship. Keller responded more broadly - "You shouldn't marry someone who will not happily go to the same church with you." The pastor was also asked what the most important aspect is when choosing someone to marry; "Besides being of the same faith, it would be someone who can forgive and repent regularly," he says.

Keller plans to release "Prayer: Experiencing Awe and Intimacy with God" this November. "It's my effort to teach people how to pray more fruitfully," he says. When asked what he would tell a younger version of himself if given the opportunity, Keller responded, "I would tell him that prayer is way more important than he thinks."

One participant asked what the most significant theological understanding that Keller, who seems to have an abundance of God-given wisdom, has come to cherish; the old saint's response was "Simply put, Grace."