Praying to an Unknown God

The belief in superior beings from the heavens is as old as ancient human civilizations. These beliefs became codified into religious doctrines that set standards of beliefs and behaviors for the vast majority of humanity living today. Each religion lays claims to their unilateral righteousness and truths to the exclusion of other religious dogmas. The consequence has been widespread religious strife over the ages. Who is this God that over half the world's peoples pray to and trust? Has anyone seen this unknown God?