Bill asked:

OK. I am wondering if fairies are real. I believe in them. I believe in angels and unicorns and Santa
Claus and hippies and giants and the Devil and God and stuff like that. I believe in peace and love
and all that stuff too. I believe that there is life on other planets and that aliens exist. Am I wack
nut???

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You may be whack nut, but I am not one hundred per cent sure. A lot would depend on how sure you
are about all the things you say you believe.

Let's go through the cases, one by one.

Fairies. There is a problem relating to the invisible variety of fairy (which most are, apparently).
No-one has ever seen a fairy, we only see what they do (for example, move stones around the
garden). The question is not so much whether this is true, but whether one has any conception of
what it would meanfor it to be true. This is one occasion when I can well see the utility of the
verification principle.

Angels. There is ample Biblical evidence for the existence of angels, from Genesis onwards. If you
are a follower of the Jewish, Christian or Muslim faiths, then you ought to believe in the existence of
angels.

Unicorns. It does not stretch credulity too far to suppose that once upon a time, there might have
existed a variety of horse which boasted a horn in the middle of its forehead. It is rather more difficult
to accept that a unicorn has the power to sense whether or not a woman is a virgin, as unicorns are
reputedly able to do. One question for the theory of knowledge is whether one would accept that
unicorns had this power, purely on the basis of an observed correlation, or whether we would require
some account of the underlying causal mechanism, whatever that might be.

Santa Claus. Obviously you don't have children, otherwise you would know where their Christmas
presents came from. To test the Santa Claus theory would require an experiment which is at least
morally questionable: namely, refuse to buy your kids Christmas presents and see if Santa Claus
brings any.

Hippies. To 'believe in Hippies' is to believe what the hippies believed in. The trouble is, the Hippies
believed in a number of things, not all of which are equally credible.

Giants. There is no conclusive proof that the Yeti and the Big Foot do not exist and never have
existed. Nor, I gather, is there sufficient evidence to conclude that they do exist or have existed.
Given, however, that there is some positive evidence, albeit tenuous, the reasonable thing to do in
this case is keep an open mind.

God and the Devil. The same thing applies to the Devil as applies to angels (see above). To believe
in 'God andthe Devil' as two independent forces neither of whom has the power to overcome the
other is the Manichaean heresy. What is wrong with Manichaeanism is not that it is heretical, but that
it provides us with a Deity whom we do not have sufficient reason to worship.

Peace and love. I believe in both of those things.

Life on other planets. It is an intriguing question why the radio telescopes have not picked up any
evidence of extra-terrestrial intelligent life. One gloomy explanation is that civilizations naturally tend
to extinguish themselves after a few thousand years — a very short period of time in relation to the
history of the universe. Hence the relatively low probability of our being around at the right time to
pick up radio waves sent out by alien TV shows.

Geoffrey Klempner