## Bill Maher to Climate Deniers: Consider the Possibility

### February 7, 2015

Cromwell’s Rule – Wikipedia:

Subjective probability is a measure of the expectation that an event will occur, or that a statement is true. Probabilities are given a value between 0 (the event will definitely not occur) and 1 (the event is absolutely certain to occur). The nearer the probability of an event tends towards 1, the more certain it is that the event will occur. The nearer the probability tends towards 0, the more certain it is that the event will not occur.

Cromwell’s rule, named by statistician Dennis Lindley,[1] states that the use of prior probabilities of 0 or 1 should be avoided, except when applied to statements that are logically true or false. For instance, Lindley would allow us to say that Pr(2+2 = 4) = 1, where Pr represents the probability. In other words, arithmetically, the number 2 added to the number 2 will certainly equal 4.

The reference is to Oliver Cromwell. Cromwell wrote to the synod of the Church of Scotland on August 5 1650, including a phrase that has become well known and frequently quoted:

I beseech you, in the bowels of Christ, think it possible that you may be mistaken.[2]

As Lindley puts it, assigning a probability should “leave a little probability for the moon being made of green cheese; it can be as small as 1 in a million, but have it there since otherwise an army of astronauts returning with samples of the said cheese will leave you unmoved.”[3] Similarly, in assessing the likelihood that tossing a coin will result in either a head or a tail facing upwards, there is a possibility, albeit remote, that the coin will land on its edge and remain in that position.

If the prior probability assigned to a hypothesis is 0 or 1, then, by Bayes’ theorem, the posterior probability (probability of the hypothesis, given the evidence) is forced to be 0 or 1 as well; no evidence, no matter how strong, could have any influence.

### 14 Responses to “Bill Maher to Climate Deniers: Consider the Possibility”

1. That speech by Palin indicates that she was on drugs. I’ve seen that happen before.

2. ubrew12 Says:

Japan’s conservatives still insist they invaded Asia in the 1930s to save it from ‘white devil’ colonialism. So, you know, if utter defeat in battle, two nuclear explosions, and a century of disgust by fellow Asian countries over their mistreatment, can’t move that conservative heart from its utter confidence in its own awesomeness, I’m not sure what hope we have.

3. skeptictmac57 Says:

People who admit that they were wrong about a previously strong belief that they once held can look surprisingly good to others, and they should not be afraid to take that step. But there is a catch to that, in that it must have been an honestly held (if erroneous) belief based on bad information.
But those who transparently push and defend wrong ideas for political, ideological, cynical, financial, dogmatic, religious (I repeat myself), and criminal, reasons, cannot easily retreat from that position and still be seen as trustworthy, except by people who share those same qualities. And to be sure, there are plenty of those out there too.

• ubrew12 Says:

It’s happened too many times that after arguing AGW on-line off and on with a particular denier, he’ll let slip something about ‘the free market’. It always comes as a shock, to be abruptly brought back to the reality that, for too many of these guys, their argument has nothing to do with the Climate. There is something, apparently, besides fossil fuel, that is as much in existential threat if AGW is admitted to be true, and its really more of an Ayn Rand faith. These guys won’t be found on the economics threads arguing their faith there, because they are up against actual experts in economics and business, etc. So they learn to clam up, and go to the AGW threads where, apparently, they feel they have a better chance of swaying some minds, not about Climate, but about economics! It’s kinda scary as to what it says about the depths of the human mind.

• Linda Plano Says:

The question I always get from deniers is, “But why should we change our behavior to avoid uncertain problems in the future when it will cost us our way of life in the present?”

I usually get on my soapbox about American innovation and entrepreneurship at that point, though I can’t say it’s been convincing.

The clean air and water acts and related regulation did not destroy our economy (in spite of dire predictions). They led to innovations that have made the US a safer, cleaner place to live and they led to new business opportunities.

To me it seems unpatriotic to say “Our economy will die if we don’t get to keep living as we do right now!” (Not to mention irresponsible not to change for all the other reasons.)

A client of mine designs amazing innovations for the developing world, then adapts them for sale in the developed world. His perspective is that “Tough constraints make better design.” http://www.haddockinvention.com/projects/clean-energy/windcell174

4. indy222 Says:

yeah…. but…. she did win a beauty contest.

5. pendantry Says:

Maybe I’ve lived a sheltered life but I think that’s the first time I’ve ever seen anyone in a popular idiot box show actually suggest that the ‘trickle-down effect’ might actually be a figment in the mind’s eye. (Personally, I think a form of it does exist: rich bar stewards use it quite effectively to convince sheeple to continue funding their greedy lifestyles.)

6. Now I will be watching for Bill Maher to live up to his own advice and do a program entitled:
“You betcha I was wrong about vaccinations”

• Perhaps he is just trying to clean up the gene pool a bit to get more anti-science people to stop taking vaccines. 😉