American Buddhist writer and academic Robert A.F. Thurman writes in Essential Tibetan Buddhism (1995,)

The enlightenment of the Buddha was not primarily a religious discovery. It was not a mystical encounter with “God” or a god. It was not the reception of a divine mission to spread the “Truth of “God” in the world. The Buddha’s enlightenment was rather a human experience of the final nature and total structure of reality. It was the culmination for all time of the manifest ideals of any tradition of philosophical exploration or scientific investigation. “Buddha” is not a personal name, it is a title, meaning “awakened,” “enlightened,” and “evolved.” A Buddha’s enlightenment is a perfect omniscience. A Buddha’s mind is what theists have thought the mind of God would have to be like, totally knowing of every single detail of everything in an infinite universe, totally aware of everything—hence by definition inconceivable, incomprehensible to finite, ignorant, egocentric consciousness.