How can I be sure that God exists?

We experienced some technical difficulties in the first few minutes of this video... sorry that we start mid sentence, but the first part of service was lost.

¹In the beginning was the Word, and the Word was with God, and the Word was God. ² He was with God in the beginning. ³ Through him all things were made; without him nothing was made that has been made. ⁴ In him was life, and that life was the light of all mankind. ⁵ The light shines in the darkness, and the darkness has not overcome it.