I will devote this essay to how we came to believe in intelligent life in other solar systems. I have done this even though belief in life in ours and life in others has often been closely intertwined. There is too much material. Intelligent life on our system's planets is a whole other essay. At the least.

There have been two main theories about intelligent life among the stars. One is that Man is the Center of the Universe. A corrupt center surrounded by the spiritual grandeur of God and the angels, but the center nonetheless. In fact, its very corruption made it the center. This conception of the universe is considered Aristotle's, whose theory of gravity – more a theory of non-gravity – inferred it. There was some controversy over whether stars and planets had souls or orbited because of spiritual beings who inhabited them. Usually angels. Aristotle originally believed the stars and planets had souls. Albertus Magnus and Saint Thomas Aquinas said it made no difference. Whether by their souls or angels, the stars and planets still orbited.

All 20th Century histories of extraterrestrials ignore this theory. I mention it because extraterrestrials have often been close to angels: without sin, more rational, sometimes with miraculous technology. The last not as often in the 18th and 19th Centuries as in the 20th Century. Miraculous technology and angelic powers were not needed because extraterrestrials, unlike angels, did not stand watch and ward over man and nature. Nonetheless, as I have shown in my last article in Challenger, the Extraterrestrials of the 18th Century were often angelic like this. The type continued into the 19th Century too. And the 20th and 21st.

One striking example is Ellen White, the founder of Seventh Day Adventism. She portrayed extraterrestrials who were angelic as well as actual angels. Ellen had a vision of the planet in the Orion nebula where God was breaking through. While on that planet, Ellen was attended by an angel. On the other hand, the extraterrestrials there were "noble, majestic and lovely" because they followed God's commandments strictly. In short, they were angels in their way. Given the hold which the past had even during the mid-19th Century, such angels had to go back to Aristotle.

The second theory is that there are intelligent beings like us in other solar systems. The idea is known as the Plurality of Worlds. In fact, there may be an infinite number of suns with planets and infinite number of intelligent beings. Originally, this theory came from the philosophers Leucippus (fl 5th Century B.C.) and Democritis (460 B.C.-370 B.C.), who, strangely enough, lived before Aristotle. It was made popular by Epicurus (341 B.C.-270 B.C.). The rationale of these Classical Greek philosophers had to do with ancient atomic theory; only later did the Plurality of Worlds get its trademark theological rationale. It is amazing how easily this originally materialistic theory became religious and mystical.

There has been a misconception that this theory is based on the facts. Lovejoy tries to correct this notion and points out that people could not know that the stars were suns until the distance was measured between our solar system and the star 61 Cygni in 1838 by Friedrich Bessel (1784-1846). The problem is worse than that. Lovejoy presupposes that that proves there are planets orbiting those stars; something we only recently have been able to observe even indirectly. And then what about intelligent life? We still have not observed that elsewhere in the universe.

We know it exists nonetheless.

The original Ancient Greek Plurality of Worlds differs from what it became in another way. The worlds in the original were not seen but unseen. And beyond the stars. A view that was taken by Lucretius (ca 55 B.C.-99.B.C.). However, I am convinced that, by the late Roman Empire, there were some who believed in other worlds in outer space – and extraterrestrials. Crowe claims that the first sign that someone, seriously, believed the other worlds were in outer space came from the Church historian Eusebius of Caesarea (fl. 4th Century). He claimed Heraclitus, the Pythagoreans and Orpheans believed every star was a world, and presumably inhabited. Their idea of solar systems here being different from ours. This statement by Eusebius is a slender reed. These beliefs are being described by someone who despised them. And who could easily have gotten them wrong. He certainly got Heraclitus' beliefs wrong.

However, I have other evidence as well, from Lucian of Samosata (120 A.D - after 180 A.D.). He lived even earlier. A part of his True Story concerns a trip to the Moon. It is true he meant his tale as a joke, to lampoon traveler's tales. In the beginning, he admits every word he has written is a lie. On his Moon, people had children from the calves of their legs and had detachable eyes. There was a giant bird the Lunarians rode on, with lettuce for wings. Nonetheless, wittingly or unwittingly, he placed the Other Worlds in outer space. I have heard that a journal of his says that he rather wittingly advocated Plurality of Worlds, but placing them in outer space was apparently unwitting. An assumption, it seems, when earlier philosophers seemed to have made the opposite assumption. There certainly are Other Worlds beside the Moon in True Story. There is a war between the Moon and the Sun for possession of the Morning Star. I wonder if Ptolemy's or others' new astronomy made it seem the Moon, Sun and the planets were more like Other Worlds and less like the Aristotelian gods, spirits or souls?

The next person I know of to place the Other Worlds in outer space was Nicholas of Cusa (1401-64), a priest. He did this in 1440. He is also known as Nikolaus Krebs, Nicolaus Cusanus and Nicholaus of Kues. Later, despite advocating the Plurality of Worlds, Nicholaus became a cardinal. He believed life, including men, animals and plants, exists in the lunar, solar and stellar regions, i.e., the Moon, Sun and the Stars. In fact, he believed all of the stars are inhabited. Whimsically, he suggested that they followed astrology. Bright, enlightened and spiritual beings on the Sun; lunatics on the Moon.

Nicholaus set a lot of firsts. His reasons for believing were not scientific in the least but fully inferred form his Platonic conception of God. And writers followed similar reasoning down to the late 19th Century. Another first from Nicholaus was that the extraterrestrials exist in a higher form than we on Earth. After saying the Solarians were bright and enlightened and the Lunarians lunatics, he had Earth people lower down and material. I have no doubt that this Platonist was taking a bow to Aristotle. As have many other who have imitated him down to the present time. A third first from Nicholaus was that, having whimsically fathered astrological attributes on them, he realized that there was no way to know who or what the extraterrestrials are. An attitude responsible people have, after flights of fantasy, returned to from his time to today.

Later, Giordano Bruno (1548-1600) also advocated the Plurality of Worlds. Which, despite folklore, apparently was not the reason he was burnt. His infinite universe was certainly different from Lucretius' and Epicurus'. All things, including the planets and the stars, were living. And all things were Divine. He advocated a very intellectual magic. And the stars influenced this magic both in demonic and angelic ways. There is another thing striking about Bruno's system: it integrated the Plurality of Worlds with Copernicanism. His planets moved around Suns not vica versa. Apparently Bruno was not the first to do this; Thomas Digges earlier fused Copernicanism with the Plurality of Worlds. And Bruno could have easily read him while he resided in England.

After that a whole array of famous people debated whether there was a Plurality of Worlds with intelligent life. Early on, opponents dominated. Between the late 17th Century and the late 19th Century, those favoring it were in the vast majority. I will list famous people you would recognize. Those famous in America only to experts, like Friedrich Klopstock the 18th Century German Milton, I will omit. Here goes the list: Johann Kepler, René Descartes, Christiaan Huygens, Sir Isaac Newton, Bishop George Berkeley, John Locke, Alexander Pope, Sir William Herschel, John Wesley, David Hume, Cotton Mather, Benjamin Franklin, Voltaire, Thomas Paine, William Wordsworth, Lord Byron, Percy Bysshe Shelly, Sir Humphrey Davy, Alfred Lord Tennyson, Ralph Waldo Emerson, Thomas Huxley, Daniel Webster, August de Morgan, Georg Hegel, Joseph Smith, and Auguste Comte.

It might be cheating to mention Auguste Comte and Georg Hegel. Their contribution was that they said in no uncertain terms they could be less interested in what happened in other star systems. However, Voltaire wrote more than dozen philosophical novels where he dealt with the moral ramification of the Plurality of Worlds. In Candide, if you read the people Voltaire was attacking, like Leibniz, you will see he certainly was doing just that. Some were skeptical of the Plurality of Worlds. John Wesley, the founder of the Methodist Church, and David Hume, the well-known skeptic, for their own purposes doubted how explicit a plan God had for the cosmos. Wesley even used scientific evidence against the Plurality of Worlds. Occasionally, we get revelations about Other Worlds. Joseph Smith, the founder of the Church of Latter Day Saints, said that his told him it was not the Earth that was closest to the throne of God but a planet called Kolob.

Two authors seem to claim the first part of Thomas Paine's Age of Reason concerns the Plurality of Worlds. As far as I can see, we are lucky if there are four pages concerning it. However, here is the famous Thomas Paine quote:

"From whence then could arise the solitary and strange conceit that the Almighty, who "had millions of worlds equally dependent on his protection, should quit the care of all "the rest, and come to die in our world, because, they say, one man and one woman had "eaten an apple! And, on the other hand, are we to suppose that every world in the "boundless creation had an Eve, an apple, a serpent, and a redeemer? In this case, the "person who is irreverently called the Son of God, and sometimes God himself, would "have nothing else to do than to travel from world to world, in an endless succession of "death, with scarcely a momentary interval of life."

Also, Daniel Webster was supposed to have lost his faith in Christianity because of the Plurality of Worlds. Other writers, like Rev. Thomas Chalmers and Rev. Thomas Dick, proselytized for religion by invoking the Plurality Worlds. Since they are not famous to us, I omitted them above.

The Plurality of Worlds was a favorite of poets. Percy Bysshe Shelly wrote in Prometheus Unbound (1820)

"Then, see those million worlds which burn and roll
"Around us; their inhabitants beheld
"My spher'ed light wane in wide heaven...."

Alfred Tennyson wrote in "The Two Voices" (1833)

"The truth within my mind rehearse
"that in a boundless universe
"Is boundless better, boundless worse...

"Think you this mould of hopes and fears
"Could find no statelier than his peers
"In yonder hundred million spheres."

In "Ode on the Death of the Duke of Wellington (1852), he wrote

"Tho' world on world in myriad myriads roll
"Round us, each with different powers,
"And other forms of life than ours,
"What know we greater than the soul?"

Now back to people you have never heard of: one in particular who fired a parting shot in the controversy, William Whewell. A famous philosopher in his time, though less famous right now, he decided that the Plurality of Worlds was irreconcilable with Christianity. That the only position reconcilable with it was that Earth was the only planet in the universe with intelligent life. He published a book claiming that in 1853. It brought much philosophy and many of the latest scientific findings to bear on the question.

And it inaugurated a great controversy. And some vituperation. Among the participants was Sir David Brewster (1781-1868), a famed scientific thinker, winner of medals from the Royal Society. He was one of those people, I mentioned, whose faith in God was based on the Plurality of Worlds. And apparently he was much in need of God right then. And very angry that someone was trying to take his faith away. He was scathing in his attacks on Whewell: "a man dead to feeling and shorn of reason," "utterly inept and illogical." "the grapeshot of assertion, banter, and ridicule,""some morbid condition of mental powers."

However, Sir David could not stop the trend, which was going against the Plurality of Worlds. And for a more scientific, and less religious and philosophical, approach to the stars. By giving as much evidence as he did, Whewell helped. Of course, while it may have proven there was no intelligent life on the Sun, the Moon, and the planets of our solar system, which the Pluralists claimed, none of it came close to proving we were it in the universe. One who, unlike Whewell, embraced the scientific approach completely was the most famous writer in England on other worlds in the decades afterward, Richard A. Proctor. On the other hand, Camille Flammarion in France kept up a religious/philosophical approach for six decades, into the 1920s. His views were far from conventional: his idea of the Plurality of Worlds included reincarnation. Still, he was popular in France and elsewhere.

However, the atmosphere was primarily scientific, and two scientific theories took over. The Buffon Theory named after the Georges-Louis Leclerc de Buffon (1707-1788). And the Kant/Laplace theory named after Immanuel Kant (1724-1804) and Pierre-Simon de Laplace (1749-1827), known also as the Nebula Hypothesis. In the Buffon theory, planets, and thus intelligent life, have been an accident. It has been the scientific replacement for the Man the Center theory. If man was not the center of the universe, he was at least the center of intelligence. In the Nebula Hypothesis, planets are formed as a matter of course from dust, planetoids, etc. It has been the scientific replacement for the Plurality of Worlds. There were other stars systems, and its proponents presumed other intelligent beings as well. These theories have competed with one another down to the present time.

The Buffon Theory, where planets around stars are rare, dominated between 1900 and 1940. Theoretically, intelligent beings were few and far between – if man was not the only one. Unlike during the Plurality period, not everyone fell into line. This trend did not seem to affect science fiction. It is true that a lot of science fiction about extraterrestrials took place where it always had, in our solar system. Certainly the Burroughs books did; and C.S. Lewis' trilogy, Wells' First Men in the Moon, and Stanley Weinbaum's Martians. However, Olaf Stapledon's Star Maker took place all over the known universe. And beyond. And David Lindsay's Voyage to Arcturus took place in the Arcturus system. The last was unpopular, as far as I can tell, because of its pessimism rather than its setting.

After 1940, the Buffon theory was replaced by a renewed Kant/Laplace theory. And I cannot help believing that in this time of "pluralism," this scientific replacement for the theory of the Plurality of Worlds would be attractive. Again not everyone has fallen completely into line, at least with intelligent extraterrestrials. It is not rare that science fiction stories and novels will have humans colonize a galaxy where humans are the only intelligent life.

Crowe, Michael J. The Extraterrestrial Life Debate, 1750–1900 (1999).

Lewis, C.S. The Discarded Image: an Introduction to Medieval and        Renaissance Literature. Cambridge University, 1964.

Lovejoy, Arthur O. The Great Chain of Being (1933), esp Lecture IV and VI.

Lucian's True Story, Excerpts-
       http://www.users.globalnet.co.uk/~loxias/lucian/vera_historia01.htm

Yates, Frances A.. Giordano Bruno and the Hermetic Tradition. University of        Chicago Press, Ltd., 1964.