If God did exist why should we believe in him? 

You have searched me, Lord, and you know me. You know when I sit and when I rise; you perceive my thoughts from afar. You discern my going out and my lying down; you are familiar with all my ways. Before a word is on my tongue you, Lord, know it completely. You hem me in behind and before, and you lay your hand upon me. Such knowledge is too wonderful for me, too lofty for me to attain. Where can I go from your Spirit? Where can I flee from your presence? If I go up to the heavens, you are there; if I make my bed in the depths, you are there. If I rise on the wings of the dawn, if I settle on the far side of the sea, even there your hand will guide me, your right hand will hold me fast. If I say, “Surely the darkness will hide me and the light become night around me,” even the darkness will not be dark to you; the night will shine like the day, for darkness is as light to you. For you created my inmost being; you knit me together in my mother’s womb. I praise you because I am fearfully and wonderfully made; your works are wonderful, I know that full well. My frame was not hidden from you when I was made in the secret place, when I was woven together in the depths of the earth. Your eyes saw my unformed body; all the days ordained for me were written in your book before one of them came to be. How precious to me are your thoughts, God! How vast is the sum of them! Were I to count them, they would outnumber the grains of sand — when I awake, I am still with you... Search me, God, and know my heart; test me and know my anxious thoughts. See if there is any offensive way in me, and lead me in the way everlasting. (Psalm 139)

On a cloudy day I entered the unfamiliar church, knelt, prayed, then scanned the ornate late 19th Century interior.

The high altar stood in a tall, narrow chancel consisting mostly of stained glass.  Various saints ascended toward a sparkling throne from which Father, Son, and Holy Spirit presided. It was a miniature Saint-Chapelle. Seven brass sanctuary lamps flickered in the dimness.  There was a slight fragrance of sandalwood, frankincense, I may have imagined the myrrh.

As the organ prelude began - maybe the Bach Fugue in C minor - I had a slightly dizzy sense.  The sanctuary lamps seemed to pulse, then they were moving toward me.

I rubbed my eyes, but if anything the lamps were closer, brighter, more vivid.

Some interior voice suggested, "You are having a mystical experience."  It had been awhile.  I was not displeased, not afraid, but I was, probably, very erect in my seat and wide-eyed.

Then I realized: the clouds had begun to clear. The chancel was oscillating between light and darkness. Each strobe of light extended my depth of vision, each cloudy dimness reduced the same in rapid progression.

I sat back with a deep sigh, both relieved and disappointed.

We are mostly creatures of sensory experience.  What we perceive is what we believe.  We are innate empiricists.

We can and ought to discipline our perceiving: extending, sharpening, testing and confirming.  We can and ought avail ourselves of the perception of others: considering, questioning, attempting to recreate, confirming or denying.

Because I have experienced God, I believe in God.