You have asked about this controversial passage (13:18) from the Revelation to John: “Let him who has understanding reckon the number of the beast, for it is a human number, its number is six hundred and sixty-six.”
The Revelation was intended, first and foremost, as a rallying cry for Christians at a time, at the end of the first Christian century, when they were being severely persecuted. It is expressed symbolically because to openly speak out against Rome would have been foolhardy. Metaphysically, it describes the inner turmoil that each of us can expect to experience as we seek to replace old, fear-based attitudes with new, Christ-centered thoughts and beliefs.
Chapter 13 is packed with references to the political realities of that time that we can only vaguely understand today. Metaphysically, however, the images speak to us clearly of the internal struggles that will inevitably be involved in our efforts to move forward on our spiritual journeys to the new consciousness that is the kingdom of heaven.
The two beasts spawned by the dragon represent those who were tormenting followers of Jesus at that time. One was the Roman Empire itself, and the other was the hated Emperor Nero, who had actually died by this time. But Nero had been such a malignant force that some people refused to believe he was really dead. There were rumors—like Elvis sightings—that he had actually escaped to the East, where he was amassing a great army that would be coming any day to lay waste to everything.
The great beasts then are our most deeply rooted fears. Some may seem rational; others are totally irrational, based on fears from the past rather than the present moment. We “worship the beast” when we develop beliefs and make choices out of the energy of fear the beasts embody.
And the number of the beast—so powerful a symbol that we avoid it in many ways still today—is 666 (or, in some early texts, 616). In both Hebrew and Greek, letters of the alphabet had numerical equivalents. Numerically, then, "666" represents "Nero, Caesar."
So our spiritual journey forward is challenged and complicated by our fears from the past—fears that have no reality even in today’s human experience, and certainly have no reality in the spiritual Truth of who we are.