Because God is. Not because I feel He is; for tomorrow I may feel differently. Not because reasoned arguments convince me that He is; for tomorrow I may begin to doubt what once convinced me. Not because I want Him to exist; for tomorrow my wants may change and God may become inconvenient. No, I believe in God because He is as obvious as the universe He has made, as near as my own thoughts, as real as His countless answers to prayer, and as true as the great and precious promises He has fulfilled to me.
I could pretend, as so many do, that He has never been, but the foolishness of that fiction is too great for me to sustain. I could shake my fist in defiance of His Soveriegnty and resolve to steer my own course, but I have only to look about me at the countless human shipwrecks to see the terrible folly in placing a blind man at life's helm. I could wall myself in with human "science" and "logic" "til I had erected a fortress unassailable, massive and immoveable. But the builders of these keeps grow cold and blinded by the very walls they erect; they are so proud of the power of their stronghold to obscure God they never realize that these same walls also imprison them.
God is. This is, as far as I'm concerned, a simple, brute fact, which no amount of denial will erase.
Selah.