[jarrett]

It's a valid question. The article takes the following premise: Parapsychology gets positive results following the scientific method as defined by prevailing norms in the scientific community. So why can't we draw the conclusion that parapsychology is as legitimate as other branches of science? What is to separate it?

I would offer a pseudo-Bayesian[1] answer to that question. Parapsychology aims to prove hypotheses that lacks theoretical foundations. Our current understanding of physics and biology weigh strongly against the existence of psychic phenomena. Even before any experiment is conducted, we must admit that psychic phenomena are unlikely to exist. Our experimental results must be evaluated in light of that prior probability.

Thus, parapsychology is and should be held to a higher burden of proof than other branches of science. We should demand more rigorous experimental designs, stronger effects, and smaller p values. This XKCD presents a similar idea, if you substitute "psychic phenomena exist" for "the sun has gone nova":

http://www.explainxkcd.com/wiki/index.php?title=1132:_Freque...

[1] I say "pseudo" because I'm not a statistician by trade. I'm basing my argument on my rather superficial understanding of Bayesian statistics. I still think it's a valid argument in its own right, but I don't claim that it's an accurate representation of Bayesian statistics.

[ChuckMcM]

Parapsychology aims to prove hypotheses that lacks theoretical foundations.

This is the lynch pin for most scientists. Before you can have a hypothesis, you must have a theory, and you can work to prove or disprove that theory by experimenting to create or observe results that the theory predicts. Parapsychology doesn't have good, testable, theories. Rather it has some interesting unexplained correlations.

[pjreddie]

Doctors rejected hand washing for a long time because there was no theory behind why it would improve patient care, even when there was overwhelming evidence showing it decreased mortality rates.

Do you discount all evidence that doesn't fit into your world view? Maybe theory hasn't caught up with evidence yet.

[kansface]

The answer of course is no. The degree to which we think its shit is related to how much we know about related fields and the size of the effect among others. The prior isn't binary.

For the topic at hand, ESP would most likely invalidate quite a bit of physics no one is questioning for other reasons and there is no proposed theory to explain the effects. Our confidence in the studies is rightfully close to zero.

[jarrett]

> Doctors rejected hand washing for a long time because there was no theory behind why it would improve patient care

The germ theory of disease and experiments supporting the theory predate medical sanitation. (Pasteur's work did come after, but he wasn't the first.) The medical community's initial rejection of handwashing was not due to a scientifically motivated demand for a sound theory. Rather, it was due in large part to doctors' unwillingness to believe that they were the ones spreading disease from patient to patient. Additionally, the medical community at the time did not embrace the scientific method to the extent that it does today. Had it, handwashing would have been evaluated in a controlled study and proven effective.

[pjreddie]

http://en.wikipedia.org/wiki/Ignaz_Semmelweis

> Despite various publications of results where hand-washing reduced mortality to below 1%, Semmelweis's observations conflicted with the established scientific and medical opinions of the time and his ideas were rejected by the medical community. Some doctors were offended at the suggestion that they should wash their hands and Semmelweis could offer no acceptable scientific explanation for his findings.

He published a lot on the subject and was rejected because it didn't fit in with how doctors saw the world and he had no theory to back up his findings. It wasn't until Pasteur that germ theory gained any widespread acceptance so it's pretty irrelevant that other people thought of it first.

Plenty of things are evaluated in controlled studies and still rejected today. For example, the article that you presumably just read discusses one such thing.