In the Ancient World, initial objects of worship of the common people everywhere were the forces of nature. Hence personifications of the forces of nature were the first gods in all the ancient cultures whether in Egypt, Mesopotomia, India or China.Thus the gods of the Sun,the Moon,the fire,the water, the wind etc. originated. In course of time, when the clans and the tribes came together to form villages and towns,in the field of religion/worship also a tendency to move from "the many" to "the few" and ultimately to "the One" came about. Then it was a natural development that one god dominated others to become The God.The Sun, as the giver of light and heat and the one who sustained life was the natural claimant to this position.An invisible supreme being was unlikely to develop as a concept in the minds of the common people.Hence it was quite natural for Akhenaton to select the Radiant Orb as the Aten, his God.It was the most intelligent selection of that period.The reason of the opposition of the priests was their fear of the possible loss of their perks and privileges.Hence the concept of Atenism was a revolutionary idea, ahead of times.