C.S. Lewis in his book (The Problem with Pain, 150), stated “There have been times when I think we do not desire heaven; but more often I find myself wondering whether, in our heart of hearts, we have ever desired anything else”.  What he’s talking about is the desire at the core of all our desiring, the thirst that is never quenched by anything we find in this world: our desire for God. 

Lewis calls this core desire “the secret signature of each soul, the incommunicable and unappeasable want, the thing we desired before we met our wives or made our friends or chose our work, and which we shall still desire on our deathbeds, when the mind no longer knows wife or friend or work” (152). 

This “unappeasable want” is a daily experience for us to lesser or greater degrees. Its presence is pervasive in our pursuits. Yet quenching this thirst eludes us in every earthly well we drink from. And nothing in this material life, or even a heavenly mansion will satisfy it either. Only One Thing will. As Randy Alcorn says, 

We may imagine we want a thousand different things, but God is the one we really long for. His presence brings satisfaction; his absence brings thirst and longing. Our longing for Heaven is a longing for God. (Heaven, 165) 

God himself is “the fountain of living waters”; apart from him every other cistern we dig will leave us dry (Jeremiah 2:13). Only he can give us the drink that will forever end our deepest thirst (John 4:14). Our unquenchable thirst, our unappeasable want, is a desire for God (Psalm 63:1–2). This is what the Bible reveals from cover to cover. 

Taken from an article by John Bloom, Staff Writer, desiringGod.org