Re: Pienso, luego Dudo – Capítulo 18b
Aca encontre la explicacion del ejemplo que dio Bunge en la charla (que era dificil de entender porque cada 30 segundos alejaba el microfono a 1 metro de su boca) (Chasing Reality, 4. Causation and Chance: Apparent or Real?, 9. Bayesianism Is Hazardous):
consider, for instance, the relation between the HIV virus and AIDS. It is well
known that, whereas those who have this disease test HIV-positive, the converse
is not true: some individuals have lived with the virus for a decade or
more without developing AIDS. Suppose then that a given individual has
contracted that virus, and that we wish to ascertain the probability that he
also has, or will soon develop, AIDS. Presumably, a Bayesian would set
Pr(AIDS | HIV) = Pr(HIV | AIDS) Pr(AIDS) / Pr(HIV). Further, since the individual
in question has tested HIV-positive, our Bayesian is likely to set Pr(HIV)
= 1. And, since it is known that whoever has AIDS also has the HIV virus,
Pr(HIV | AIDS) = 1. Thus, Bayes’s formula simplifies to Pr(AIDS | HIV) =
Pr(AIDS). However, this is known to be false: in fact, HIV is necessary but not
sufficient to develop AIDS. So, if AIDS researchers were to adopt Bayesianism,
they would not try to discover the causes that, jointly with HIV infection, lead
to AIDS.