How can I know God exists?

In the course of my work I will sometimes be asked by a person one of the most difficult questions to answer, how do I know God exists? I always admit it’s not the easiest question to answer especially in just a single sentence, however I do find this short illustration might helps

If you put a buzzard in a pen six or eight feet square and entirely open at the top, the bird, in spite of his ability to fly, will be an absolute prisoner. The reason is that a buzzard always begins a flight from the ground with a run of ten or twelve feet. Without space to run, as is his habit, he will not even attempt to fly, but will remain a prisoner for life in a small jail with no top. The ordinary bat that flies around at night, a remarkable nimble creature in the air, cannot take off from a level place. If it is placed on the floor or flat ground, all it can do is shuffle about helplessly and, no doubt, painfully, until it reaches some slight elevation from which it can throw itself into the air. Then, at once, it takes off like a flash. A Bumblebee if dropped into an open tumbler will be there until it dies, unless it is taken out. It never sees the means of escape at the top, but persists in trying to find some way out through the sides near the bottom. It will seek a way where none exists, until it completely destroys itself.

In many ways, there are lots of people like the buzzard, the bat and the bee. They are living their life with all their problems and frustrations, not realizing that the answer is right there above them. All we need to do to begin the answer to our question about God is to begin to look at life through the eyes of faith and then we may be able to see that God can be found as we begin to look in the right directions. Symbolically we need to look up, away from ourselves to look to heaven, not that heaven is literally above us but to realise that the Kingdom of Heaven (God) is actually very near and we access it by faith in believing the good news about Jesus Christ.