What does it mean to exist as a person in this world? 

Existentialism contains many variations. This philosophy is built primarily upon the question, What does it mean to exist as a person in this world? The focus on the predicament of a human being tends to be pessimistic and atheistic, although there are other forms that are more optimistic. The bottom line is this: It tends to see man in a mood or an atmosphere of despair. 

Man in his existence is a useless passion, meaningless and insignificant. In this view, with respect to God, the idea is that in heaven there is nobody home. This produces fertile ground for preaching the gospel, because Christianity is so optimistic. We believe that human existence is meaningful because Christ has defined the significance of our existence. God knew us before we were even born. The more we surrender to Him, the more active He will be in our lives.

Jeremiah 1:4-5

Then the word of the LORD came to me, saying: “Before I formed you in the womb I knew you; Before you were born I sanctified you; I ordained you a prophet to the nations.”

Cited Sources:  Now, That’s a Good Question by R.C. Sproul