+1 Terry Pratchett Wizards don't believe in gods in the same way that most people don't find it necessary to believe in, say, tables. They know they're there, they know they're there for a purpose, they'd probably agree that they have a place in a well-organised universe, but they wouldn't see the point of believing, of going around saying "O great table, without whom we are as naught." Anyway, either the gods are there whether you believe in them or not, or exist only as a function of the belief, so either way you might as well ignore the whole business and, as it were, eat off your knees.

Saying you don't believe in Satan because he doesn't live underground seems like quibbling to me. A lot of people thought supernatural beings literally resided in the heavens, back in the day.

And that's what it basically means for the Beast to be an alien. It's from space. It's a supernatural entity as old as creation that comes from space instead of Hell, but that's the only distinction.

@Adamant: The important point is that it ISN'T supernatural, just as for instance a giant squid isn't, however exotic it might seem to land-based mammals.

@jamesqf - It sure could have fooled me. It's like Superman - the only thing scientific about him is writer fiat.

@Adamant This is already a show about a spacefaring, time-travelling, body-transforming, immortal being who happens to end up on Earth between 1850 and 2100 a stunning proportion of the time. The only thing scientific about any of it is writer fiat. The Doctor presumably doesn't believe the religious trappings that go with "Satan", even if based on a real thing. I don't believe that Captain Jack Sparrow is a real person, even while I believe that Johnny Depp exists.

@Adamant: But there are "scientific" explanations for Superman, within the context of the fictional universe, of course.

@jamesqf - Ofc, but magic doesn't become science just because some less-than-expert writer says it's so.

@Adamant magic becomes science with discovery. The doctor discovered the truth. This seems very logical to me. I would also say I don't believe in the devil, just a big beast that people call the devil. I don't believe the stories about what happened or his origins, just his existence.

@Aethenosity - And I don't believe in Stonehenge, just a big circle of rock that people call Stonehenge.

@Adamant exactly! You believe in the stacked rocks, not the mystical background. It's really simple to understand is it? Just took you a minute. Well, cheers.

If any of us found a big magical red chap who possessed people, was the origin of "sin", and had been imprisoned by the forces of light from before creation, we wouldn't be saying we weren't big believers in Satan.

@Aethenosity - No, actually the argument sounds a bit silly to me, and that's an example. I think all this is just some serious semantic gymnastics to try to pretend that Satan isn't Satan. That's why I accepted the other answer, because it makes the Doctor seem more rational.

@Adamant oh. You don't understand the difference between.... say, a guy with a beard calling himself jesus, and the actual son of God coming to earth to solve our mortal sins? Or between the actual area called the Bermuda triangle, and the mystical powers people attribute to it? There are two levels of belief for all these things. The doctor has the lower level of belief, not the higher. It is VERY simple, and not silly at all. Just logical. But comments aren't for discussion, so bye.

@Aethenosity - I don't know if you watched the episode, but in this case the Beast actually has the mystical powers.

@Adamant I have. About 8 times now. It has powers yes. So do MANY aliens in the show. Does that mean it is actually the devil, and all the stories about the apple in eden and whatnot are automatically true? The doctor says no. Just another alien with powers. Been there seen that, why would that mean that God and everything in the bible are suddenly real. Makes more sense that the stories (which the doctor doesn't believe in) were based on truth, then warped and changed over time to something different. The doctor doesn't believe that something different. He doesn't believe the bible.

@Aethenosity I don't know whether God exists in the Whoniverse, or the Garden of Eden or whatever.

But Satan sure does.

Whether or not it tempted Jesus or Job or bought the souls of blues singers at the crossroads.

The Beast is more than Satan, since the episode implies that its mental influence has inspired other, similar, evil entities on other planets.

But it also seems rather likely to be Satan in all the important senses.

Claiming the Beast must be Satan because it's likely what inspired the myths is like finding driftwood in Loch Ness and saying you found the Loch Ness monster. Even if that driftwood is what everyone saw and what they described, it doesn't make their personification or lore around it fact. In fact, you'd find the driftwood and say "aha! This is evidence that the Loch Ness Monster probably doesn't exist! People probably saw this natural thing and gave it a supernatural element!"

And the Beast isn't necessarily supernatural; there's no reason to assume he is. His origin, identity, and purpose are all told to us simply through him. Why trust alleged Satan's word? Sure, he knows some things he shouldn't be able to know, but that's not too crazy for a Whovian creature. He can control people, but a perception filter can prevent you noticing a whole building. The Silence can erase memories. Are any of those so different? Heck, the thing in Midnight even influences the Doctor

@LordFarquaad - If the Sun in the Whoniverse is alive, has great powers, and inspired the stories of Helios...

... Yes. It would be pretty fair to call it Helios.

In answer to your second point, the Beast is no more supernatural than the Silence, the Time Vortex, the Guardians of Time, and so forth.

Which is to say, preeeeeetty supernatural.

The issue is that your piece of driftwood has very little in common with the Loch Ness Monster (which by the by also exists in Doctor Who, apparently).

But the Beast has a whole lot in common with Satan, starting with likely being the thing that people called, ending with sharing a great deal of mythological Satan's personality, MO, powers and origin.