"WHO THE DEVIL IS THE DEVIL?"  By Robert Wernick,  Smithsonian,  October 1999, pp113-123(Excerpts,with brief comment by JNR):

With the rapid approach of the third millenium, many people can't help wondering what role the Devil will be playing in it. . . . Saint Augustine said, "The human race is the Devil's fruit tree, his own property, from which he may pick his fruit."  Try to put yourself somewhere in Western Europe in the year 999, as the second millenium was about to bow in. In the tenth and for at least half a millenium thereafter, the Devil was everywhere. He leered out of every church door, and his plots and pranks and temptings of humans were spelled out in sermons, on the stage, in paintings, in pious books, and in stories told in taverns or in homes at bedtime. Stirred up conspiracies and treasons. . . . He caused boils, plagues, tempests, shipwrecks, heresies, barbarian invasions. Whatever he did, his name was on everyone's tongue, and he went by many names: Satan, Lucifer, Beelzebub, Belial, Mastema, the prince of Darkness, the Lord of Lies. In the Bible the Accuser, the Evil One, the Prince of the world. Today, few hundred years later, 48 percent of Americans believe in the existence of the Devil, and another 20 percent find his existence probable. . . . Though they use him often enough in common lighthearted expressions (give the devil his due, the devil is in the details) and in the privacy of their hearts may put the blame on him when they covet their neighbor's wife, or cheat on their income tax, (or "park" their taxable business profits in some offshore banks in the Cayman Islands-jnr) they do very little talking about him out loud. . . .In practical terms, people have banished him from the public life.  Yet most everyone who discuss moral standards in pulpits or on television talk shows or in the New York Times is agreed that morals are lower than ever before. . . . Where has he gone? It all depends on precisely what you mean by "the Devil."  Today, the average person with no theological axe to grind is apt to envision the Devil as a sleek, dark-complexioned male figure, with black chin-whiskers, little horns and clover hooves, perhaps with a foxy glint in his eye and a trace of foreign accent, but on the whole handsome, worldlywise, a persuasive talker, a friendly sort of customer. He may tell you anything, try to talk to you into something too good to be true. Only later, when you've taken that risky bet or signed a shady contract, and he comes to collect his due, do you realize you have signed away your immortal soul. He is unquestionably the Lord of Lies.

The God of ancient Greece are typical: Zeus was a wise ruler up on Mount Alympus, but he became a serial rapist when he came down to the lowlands; Persephone was goddess of life in spring and goddess of death in autumn. None of these ancient religions ever developed a single Devil concentrating all the essence of evil, any more than they ever concentrated on the essence of good in a single God. The Old Testament. . . .has little trace of the Devil with a capital D, and in its earliest books, none at all. God speaking through Isaiah says,"I form the light and create darkness, I make peace and create evil, I the Lord\\ do all these things." The serpent who tempted Adam and Eve was later identified by Jewish rabbis and Christian church fathers with the Devil, the principle of Evil; but in the third chapter of Genesis as written, he is only a snake. It took another few hundred years before both snake and Devil were identified with Lucifer ("light-bearer," the Latin translation of the Hebrew and Greek words for the morning star, the planet Venus).

The first Devil, the first concentration of all evil in a single personal form, appears in history some time the sixth century B.C., in Persia. His name is Ahriman, described by the prophet  Zoroaster (Zarathustra) as the principle of Darkness (evil) engaged in ceaseless conflict for control of the world with Ormazd or Mazda, the principle of Light (good).
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The next few centuries of the so-called Intertestamentary Period between the compilation of the Old and New Testaments, when a major subject of theological speculation and literature was the apocalypse - the final struggle between good and evil at the imminent end of the world - this Satan grew in stature as the leader and embodiment of the forces of evil.
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One of the most popular stories throughout the Middle Ages, retold hundred times in many European languages was that of Theophilus of Cilicia, a sixth-century ecclesiastic who signed a pact with the Devil, exchanging hisnsoul for a powerful profitable position in the church. he was then able to lead a life of unbridled pride and corruption.... Theophilus, eventually repented and threw himself on the mercy of the Virgin Mary, who took pity on him, descended into hell, grabbed the pact from Satan, then interceded for the sinner at the throne of God. He was pardoned, and the Devil was cheated of his due. This tale played a major role in establishing the cult of the Virgin in Catholic Europe.
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To this day we can ask is the Devil dead, or he is just hiding somewhere? Professor Delbanco and Prof. Jeffrey Burton Russell, of the University of California in Santa Barbara both claim America has "lost its sense of evil, and without a sense of evil a civilization must go straight to Hell." Perhaps, he is not dead after all; he may only be in hiding, and he could appear and be active anytime and anywhere where the opportunity comes.Those devils may not neccessarily be what people think, but they could be any person in flesh and blood, like you and me, as we noted in the history of our civilization.

Madame Carmelita, a psychic on the Upper East Side of Manhattan, has assured me that the world will end on or about my 100th birthday, February 18, 2018. Or a scientist has assured me that the world (meaning life on earth) will come to an end when our sun becomes a red giant in the year 4,000,000,999. If in the meanwhile a sleek gentleman dressed as a prosperous options-and-derivatives salesman offers you fantastic odds on a bet that he will not be  around right up to the last second on any or all of those occasions, and you take him up on it, you will probably be making a bad bet.