Recently I've seen several web site using the term 'denialism'. They,
for the most part, provide a good insight into the phenomenon.
However, a fallacy I have seen in that all of these appear to
indiscriminately label right-wing politics 'denialism', weakening the
force of their arguments. I'll try to start from scratch.

First let's name a few examples of denialism, ones that everyone
should agree to be so. One of them is the one people usually associate
with the term - Holocaust denial. It is often thought that Holocaust
deniers are just lying for anti-Semitic purposes; I don't buy it.
While most of them are anti-Semites, they honestly do believe it.
Another is AIDS denial; this may have started as a scientific theory
but quickly became a kind of denialism.

The third example is creationism, at least in the expositions that
most people are exposed to. What do these have in common? It is that,
from the perspective of someone acquainted with the facts, they appear
to be blatantly lying, yet they think they are being honest. They have
a pre-conceived idea that, for whatever reason, is held so strongly
that it distorts their thinking - all facts are interpreted in the
light of the idea, and either ignored or twisted to fit the theory.

Let me now turn to the second part of my title. Crank theories are
familiar to every scientist. Crank theories are those that start from
premisses wildly at variance with reality, but the crank can't see
this. He believes himself to be a genius and anyone that disagrees to
be simply ignorant.

What is the difference between crankery and denialism? It is, I
believe, the motive of the proponent. The crank has faith in his
_mind_ and espouses the idea fundamentally because it it his; the
denialist has faith in his _feelings_ and espouses the idea
fundamentally because he wants to believe it for non-rational reasons.
Cranks, therefore, tend to be more intelligent than denialists. Other
differences can be found, too. Cranks are almost always male,
denialists are about equally men and women (This is no doubt due to
the male superiority for abstract thinking; crankery being a bad
effect of that.) Cranks often have invested considerable time and
effort in working out their theories, while denialists do not invest
any such effort until challenged. They have in common that they both
tend to hypothesise conspiracy theories to explain their lack of
success in convincing others, and very seldom will abandon their
beliefs.

What about conspiracy theories, in the common meaning? The originator
of conspiracy theories normally have the motivations of a crank, while
the followers of one those of a denialist. This follows from the
definitions. While a denialist usually does not invent a theory as
complex as most conspiracies, and has no motivation to do so, he is
quite willing to follow an existing theory that appeals to him in some
way and thereafter looks at all other related facts through his
denialist glasses. The crank, on the other hand, is quite willing to
invent comprehensive theories once he gets an idea, but has less of a
motive to join another crank's theory, because it doesn't feed his
ego. They can overlap, as for example in those that dissent from
global warming. A few people with that idea have crank motivations,
more have denialist motivations, some have both, but the majority of
ordinary people have neither and simply don't investigate the topic in
any detail.

There are more denialists than cranks simply because denialism
requires no intellectual powers, while crankery does require some - or
at least enough to convince one that one is a genius.

One more example requires addressing. This is Langmuir's 'pathological
science'. This seems to have more the motivation of a crank, while
adopt the methods of denialism. The difference, though, is that most
scientists that have pathological ideas eventually do abandon them, if
much more slowly than they should. This is no doubt because of their
lack of the emotional involvement that denialists have. It should,
however, be considered as a type of crankery rather than denialism,
because we know many examples of scientists that crossed the line into
crankery on some issue, while I know of no real scientists that became
honest denialists.

Andrew Usher