Tuesday, 20 December 2016

Reasonable radical disagreement

Some people believe that anyone who disagrees with them is either evil or stupid. Such people deny that it is possible for there to be reasonable disagreement. Many people would reject that but believe than anyone who disagrees radically with them is either evil or stupid. Such people deny that it is possible for there to be reasonable radical disagreement. This last position appears to be held by significant portions of Trump, Clinton, Brexit and Remain supporters. All of these people are wrong. Here is why:

Sunday, 18 December 2016

Motte and Bailey Doctrines

One of the difficulties of getting people to behave better epistemically is that, whilst intellectual dishonesty is wrong, it is difficult to convict people of intellectual wrongs. As David Stove showed in his wonderful paper ‘What is Wrong with Our Thoughts?’ (The Plato Cult and Other Philosophical Follies Chapter 7 here), there are indefinitely many ways of cheating intellectually and for most there is no simple way to put one’s finger on how the cheat is effected. There is just the hard work of describing the species in detail.

Some time ago I wrote a paper entitled The Vacuity of Postmodernist Methodology (here or here or here) in which I described and named a number such cheats that I detected in postmodernism. One of these I named the Motte and Bailey Doctrine. There has recently been a flurry of use of this concept to analyse ethical, political and religious positions (e.g. here, here,)  so I am taking the opportunity to have a look at it again.

VW cheating like Obama

Nothing annoys the plunderers more than when the producers try to get away with the tricks that they have reserved to themselves. I pointed out one such instance some time ago (Penzions and Politicians http://blog.practicalethics.ox.ac.uk/2011/01/politicians-and-penzions/) and we have another one before us in the VW scandal.

No fortune of birth.

Suppose you are born with valuable talents or to wealthy parents. What is added if we say that your talents or wealth are a fortune of birth? I say, nothing! This is merely a misleading way of repeating that you were born with good possessions. It is misleading because it seeks to insinuate what requires proof and in fact, as I shall now show, cannot be proved.

Oppressing smokers for fun and profit

According to an article in the New England Journal of Medicine (http://www.nejm.org/doi/full/10.1056/NEJMra1308383),
Tripling tobacco tax globally would cut smoking by a third, and prevent  200 million premature deaths this century from lung cancer and other diseases. http://www.cancerresearchuk.org/about-us/cancer-news/press-release/tripling-tobacco-taxes-to-prevent-200-million-premature-deaths
This should, of course, be instituted immediately. It is almost the perfect public policy: self-interest dressed up as sanctimony. Not only will we make the lives of non-smokers better at the expense of smokers, but we can do so whilst telling smokers we are doing it for their own good!

Political speech crime

In an article at The conversation https://theconversation.com/is-misinformation-about-the-climate-criminally-negligent-23111 Professor Torcello has proposed that ‘an organised campaign funding misinformation ought to be considered criminally negligent’. I am wholly in agreement with him. I cannot think of a political party whose campaign can be characterised as anything other than an organized campaign funding misinformation and I would be delighted if we could bang them all up in chokey for it and be rid of them. Sorry, what’s that? He wasn’t talking about politicians? Well what was he talking about then?

Abortion on the grounds of sex

Apparently some UK doctors have been aborting babies because their parents don’t want a baby of that sex. In response the government is now planning to outlaw abortion on the grounds of sex http://www.telegraph.co.uk/news/uknews/law-and-order/11217504/Doctor-to-appear-in-court-in-UKs-first-gender-abortion-prosecution.html. It is already illegal, however, so we must wonder what the politicians are up to. A question being ignored is whether it is even wrong to abort on the grounds of sex.

Free the trolls.

You do not have a right not to be offended,  insulted or verbally abused. You do not have that right because it might be right to offend, insult or verbally abuse you. You might believe stupid things, or even sensible things, and take offence at any and all critiques, rebuttals and refutations. You might be a pompous prig, a sanctimonious sop, an officious orifice. Even if you are not these things, there would be very little wrong in telling you you are. After all, you are not a six-year old child: you’re an adult. You can take it.
What of someone expressing their detestation of you, their hatred of you, wishing you ill, wishing you dead?

Rationality and the Scottish referendum

One argument that has been put forward against voting for Scottish independence in the Scottish referendum is that it would be irrational for Scotland to break free of the rest of Great Britain. The grounds for this claim are that the Scottish economy would be significantly worse under independence. This is an empirical claim and for the sake of argument I am going to grant it. What I am interested in is whether, supposing it to be true, it would in fact be irrational. There are a number of things seriously wrong with this inference.

Politicians and Penzions

Aren’t you glad you’ve got a state pension! I know I am. It’s just great to know the government cares about us and will look after us in our old age. Kind of like having parents, only better because it’s even bigger and even stronger, and not selfish like parents are. (Also, more likely to be around at that point.) And it works so well too. You just pay money in and later you get more out. I know this because I can see pensioners getting their money out now. Obviously the money is properly invested and gives an excellent return. So I simply cannot understand why the party poopers are maundering on about dangerous pension liabilities leading to unsustainable government deficits and debts. Don’t they believe what the prime ministers and presidents tell us?  (You tube cartoon version)

Conspiracies against the laity part 3298: the medical profession.

Well wouldn’t you know it. A surgeon who transmitted antibiotic resistant superbug during operations on people’s hearts doesn’t want you to know he did.

Apparently John Chen Lu ‘a heart surgeon who infected 11 of his patients with a lethal bug, five of whom died, has taken his fight to keep his past secret to the High Court as he claims revealing the full history is “irrational” and will end his career.’ http://www.telegraph.co.uk/health/healthnews/10658014/Surgeon-who-transmitted-lethal-heart-bug-fights-to-keep-past-secret.html. (By the way, one of the joys of this article is to see the journalist mis-spell ‘principle’  over and over again.) Now I’m not very interested in the facts of this case. Mr Lu claims he is no greater risk to patients than any other heart surgeon now he has been cleared of antibiotic resistant strain of staphylococcus epidermidis. Some senior colleagues apparently do not agree and the relevant Hospitals trust has placed relatively onerous conditions on him returning to surgery. I’ve no idea, but none of this really matters. What really matters is the general secrecy of the medical profession about the quality and performance of doctors.

Time to stop the abominable illegality of kidney markets

Do you like the ambiguous title? No, I don’t think illegal kidney markets are intrinsically abominable. Insofar as they are abominable in various respects it is entirely a further consequence of the abominality of making them illegal. The abominable politicians who passed the law and sustain the law are to blame for thousands of deaths every year.
A fundamental argument for a market in kidneys is that they’re my kidneys and it’s up to me what I do with them, so keep your nose out of it. I would also direct you to an earlier argument of mine based on the ultimatum game, in which I show that if it is true that the offers in that game should be fair, then failing to pay donors for kidneys is unfair. http://blog.practicalethics.ox.ac.uk/2010/10/kidneys-and-the-ultimatum-game/ But perhaps you’d prefer an argument based on better consequences. Let me give you one:

In praise of insult

You have no right to be free from insult. Indeed, sometimes you may deserve to be insulted. Let us take a case that brings this into sharp focus: the Tory chief whip who lost his job because… well, we still don’t know exactly why because it now turns out that what the police claimed at the time wasn’t true. And maybe he should have lost his job: I don’t know. But one of the underlying assumptions throughout seems to have been that nobody should ever be sworn at. And that is flatly false. Sometimes people deserve to be sworn at. People in power deserve it when they stupidly, arrogantly or indifferently muck up our lives, something they do routinely. They deserve it most especially when they misuse their authority, such as when they do so to display their power by make someone’s life worse or for the purpose of getting  their own back on someone who resists their misuse of power.

Closing down comments

Popular Science http://www.popsci.com/science/article/2013-09/why-were-shutting-our-comments has decided they will no longer permit comments on their new articles. If you are a ‘vexing commenter’, a ‘shrill boorish specimen’, rather than a ‘delightful, thought-provoking commenter’, it now turns out you were never welcome. Of course, they have a perfect right to close their comments: it is their website. Their reasons for doing so, however, show a distressing lack of respect for the value of free speech and free opinion.
It is true that some people are shrill, boorish and vexing, but some people are merely called that because they are saying things others do not wish to hear. Climate skeptics are frequently dismissed in these terms. Very good, you might say. But so were abolitionists, feminists and gay rights activists. This is that well known irregular verb, I am forthright, you are argumentative, he is boorish, she is shrill, we are reality based truth speakers, ye (you all) are clamorous and they are vexatious liars.

Government is good for you so do what you're told!

We are discussing Huemer’s argument against political authority, where political authority is the special right of government to command and coerce what other agent’s may not and the special duty to obey what government commands. A number of commentators here have responded to earlier parts of Huemer’s argument against political authority by citing benefits of government. Heumer calls this kind of defence consequentialist, not because it requires a commitment to consequentialism (that the rightness of an act is determined solely by its consequences), but just because it is offering a justification of political authority on the basis of good consequences. The essential difficulty for this defence is that political authority  is supposed to content-independent, comprehensive and supreme, but neither consequences alone, nor consequences combined with fairness, can justify such authority.

We voted that you should pay, so pay— or else!

Previous posts in this line: http://blog.practicalethics.ox.ac.uk/2013/02/political-authority/, http://blog.practicalethics.ox.ac.uk/2013/03/what-social-contract/, http://blog.practicalethics.ox.ac.uk/2013/04/so-what-if-i-would-agree/

So runs Huemer’s initial example in considering whether political authority is justified by democracy: you’re out with a group of people at a restaurant and when the bill comes someone suggests you pay, and the motion was carried on a vote. Since we do not think this would be right, nor do we think you’d thereby be under any obligation to pay, it is clear that anyone who thinks democracy justifies political authority has to explain why what is wrong here is right for a democratic government.

Just give me the Humbug

We’ve all had fun hating Goldman Sachs again after one of their own sold them out http://www.nytimes.com/2012/03/14/opinion/why-i-am-leaving-goldman-sachs.html?_r=4&hp=&pagewanted=print. Mr Smith says that ‘culture was the secret sauce that made [Goldman] great and allowed us to earn our clients’ trust for 143 years’ whereas now Goldman pursues its own interest rather than its clients’ due to a ‘decline in the firm’s moral fibre’…. Hold on. Yes, I know its hard not to burst out laughing. …. Good. Yes, OK, so, where was I?

So what if I would agree?

The next justification of political authority that Michael Huemer considers in his book The Problem of Political Authority is what is called Hypothetical Social Contract Theory. The broad idea is that what justifies political authority is that you would agree to government coercion were you not the irrational, selfish and ignorant fool that you are. My inclination when addressed in such a manner is to say, so what? Grant that I am the irrational, selfish and ignorant fool that you say I am, why does what I would agree to if I were otherwise make it right for the government to force me to do what I don’t want to do?

What social contract?

As I said last time, I’ve been reading Michael Huemer’s book:  The Problem of Political Authority. The problem of political authority is the problem of justifying coercion by the government when common sense morality rules out the same behaviour done by anyone else. The point here is that government has no special right to command and we have no special duty to obey unless what the government does that goes beyond what we may do can be justified.
Government coercion is commands backed up by the threat of deliberate physical harm up to and including killing. In short, and for example, taxation is demanding money with menaces, morally forbidden to you and me but done by the government. Does the government have any such right and do you have any duty to obey it?
The first kind of justification Huemer considers is the social contract: that you agreed to being coerced by the government. Now I don’t know about you, but I never made any such agreement. So on that basis the government should leave me alone, shouldn’t it?

Political Authority?

An underlying assumption of much debate on this blog is that the government has the right to boss people about and the question at issue is merely which bit of bossing about the government should be doing. Despite the fact that the left are obviously very keen on bossing people about, this assumption is one I have always seen as rooted in a certain kind of right wing political philosophy, a philosophy based in the idea that people are necessarily subjects of a sovereign. To be is to be ruled.
An originating thought underlying republicanism is that one man cannot legitimately rule over another. Taken all the way, this thought will take you  to anarchy. So, must you obey the bossing about and if you refuse may they make you?

Roman Catholic doctrine and abortion

Vice-President Biden is a Roman Catholic. In the recent debate with Congressman Ryan he was asked his view of abortion and he said
I accept my church’s position on abortion…. Life begins at conception. That’s the church’s judgment. I accept it in my personal life. But I refuse to impose it on equally devout Christians and Muslims and Jews…I just refuse to impose that on others.
So he’s saying that abortion is murder and while he’s certainly not going to be murdering any babies that he’s carrying he’s cool with you murdering yours. Or am I being unfair?

Dangerous Doctors and Immoral Doctors

In general, if you know someone to be a danger to others you have a duty to do something about it. Exactly what you are obliged to do depends on the person, the situation and you. At the very least you ought to warn others.

In general, and apart from such basic duties as not to interfere with others (more pompously, to respect their autonomy), to keep your promises to them, not to harm them and not to burden them, your strongest duties are those you take on voluntarily, such as those you acquire by taking up a profession.

The professions hold themselves out to us as entitled to special privileges because of their special knowledge. We trust them, we rely on them, we place ourselves in their hands for specific purposes, because when paid for their work they promise to look after our interest before their own. Part of that promise is a special duty to hold members of the profession accountable to professional standards and to exclude persons who fail those standards.

So members of the medical profession have both a very strong duty and a special duty to protect us from dangerous doctors. A book has come out showing that doctors are grossly— indeed, grotesquely —derelict in this duty.

Lie detectors and epistemic duty

The British government is about to introduce compulsory lie detector tests for sex offenders released on parole. http://www.telegraph.co.uk/news/uknews/crime/9414112/Sex-offenders-will-take-lie-detector-tests-to-keep-a-check-on-them.html  The British police want to use lie detectors in the detection of crime. Is this the right thing to do?

Honesty and Science

Honesty is a virtue. The strange thing about honesty is that we do not seem to see even the simplest aspect, telling the truth when it is owed, as a duty. People who would be horrified at hurting anyone will trim, twist, exaggerate and lie at the drop of a hat, especially when it advances their ideological agenda, and will not feel they have done much wrong at all. Worse, they will anathematise those who utter inconvenient truth and feel highly righteous in doing so.

Shutting people up

You will no doubt recall that some time ago I was bewailing the backwardness of Britain when it comes to shutting people up who disagree with me. I think the case in point was in Austria, where the authorities were prosecuting a woman for criticising Islam. Our betters in the European Union have continued to show us the way. More recently we have the prosecution of the Danish historian Lars Hedegaard for claiming that Muslim women are subjected to sexual violence.

On the summary execution of murderous tyrants and the good of a timely accounting.

Despite my dislike of capital punishment I find it hard to object to the summary execution of murderous tyrants such as Gaddafi. A short period of terror followed by a swift ignominious death is much less than they deserve. What they deserve are the torments of hell. Nor is the absence of a trial an injustice done them—what doubt have we of their guilt? If they are a focus for forces intent on reviving their tyranny, and those forces will dissipate or fail without them, killing them may also be a benefit and even a necessity. So if there is anything wrong in their summary execution it must be found elsewhere and must outweigh the risks of keeping them alive. It seems to me there is something to be said on this other side and it is to be found in the good of a timely accounting.

Evidence on Evidence Based Policy

You were no doubt as surprised as I was when the Blair government announced it was henceforth doing evidence based policy. It was just like when the medical profession said it was going to do evidence based medicine. You mean—they weren’t already? Still, even though the promised reform doesn’t really sweeten the bitter truth, it is a move in the right direction. Or at least, it a promise to take a move in the right direction. But was the move taken?  When it comes to the, perhaps minor, example of speed cameras, we have clear evidence whether the policy was evidence based. And the evidence says, No!

Banks: Liberty or Regulation

Gordon Brown has just said that he made a big mistake about financial regulation. His remarks are in line with many politicians on the financial crisis: regulation failed therefore we need more regulation. But do we?
Frideswide Square is a notorious traffic junction in Oxford, and it’s a nightmare. It has about 20 sets of traffic lights and small problems here lead to long tailbacks in many directions, tripling journey times for many otherwise short trips. So you can imagine how awful it was when the traffic lights all broke down recently.
Except it wasn’t.

Wikileaks Rights and Wrongs

Would it be a good thing if, far from crushing Wikileaks, governments were required to post their entire correspondence on Wikileaks? In principle, this would appear to be highly desirable. A legitimate ruler over us might justifiably keep secrets from us—but there is no such thing, neither leviathan nor the general will nor the people. Government is merely a mechanism we employ to protect our rights and resolve certain coordination problems. The government is therefore our agent and agents have no ground for withholding information from principals. The enormous power accumulated by the state should not be wielded in secrecy. Furthermore, when we give up democratic and political romanticism the attractions of openness only increase: we realise that anyone putting themselves forward to have power over us (always for our own good, of course) thereby raises a doubt over whether they should have it, and that politicians are not and never will be especially wise or good and will do what they think is required to hang onto power.

Kidneys and ultimatum game

Frequently in life there is some good available, which would be an increase in total welfare, if you and I can agree on some split of that good between us. If we cannot agree the good never comes into existence and there is no increase in total welfare. This fact can be modelled by what is called the ultimatum game. In the ultimatum game somebody offers us £100 to split between us just in case we agree on the split. The rule is that I get to propose to you a split and you can accept it or reject it. So if you reject it we both get nothing. Since you are better off whatever positive offer I make, it looks as if it is rational to accept even as little as £1. 

When the game has been run as an experiment it has been found that people prefer to get nothing rather than accept low offers. Furthermore, offers that are much less than £30 are widely thought to be unfair and making very low offers is thought to be morally wrong. So a principle that seems to be being applied is that in such situations I am morally required to make an offer that divides the good roughly equally—perhaps somewhat to my benefit, perhaps as much  £70 to me and £30 to you—and morally forbidden from offering you a very low proportion. Good. If that is right then kidney recipients are morally required to offer kidney donors roughly half the good of receiving a kidney, and the law against the market in kidneys is morally forbidden and must therefore be repealed.

Ethics and Economics

The failing of economics have been widely discussed in the last few years, and now Professors Kim and Yoon have suggested in the Financial Times that ‘an eminent philosopher…should be appointed to take charge of economics’ http://www.ft.com/cms/s/0/32c10a50-a8c3-11df-86dd-00144feabdc0.html. Don’t all rush at once. I doubt they really mean it. And even if they do, we mustn’t fall for our own propaganda: philosophers don’t exactly have a good track record on practical matters.

Organs and obligations

Simon Rippon has recently argued here that markets in organs lead to harms, harms which may be outweighed by benefits, but which must nevertheless be taken into account in deciding whether such markets should be legal. He has argued that there are harms to specific third parties and harms to society at large. I’m not persuaded by his arguments that these harms arise.

How wrong may we be?

Consider these propositions:
1.        Mandatory licensing of professional services increases the prices of those services.
2.        Overall, the standard of living is higher today than it was 30 years ago
3.        Rent control leads to housing shortages.
4.        Third World workers working for American companies overseas are not exploited.
5.        Free trade does not lead to unemployment
6.        Minimum wage laws raise unemployment
Do you think they are true or false?

Are addicts addicts?

I think it would be fair to say that, insofar as people think about it at all, most people think that being an addict is a property some people have. Just like people can be tall or friendly or wealthy, people can be addicts. Some people even think that being an addict is an essential property of some people— that is to say, it is a property that they cannot lose without ceasing to be. This seems to be the view of Alcoholics Anonymous, who hold that even though an alcoholic can cease drinking, they never can cease being an alcoholic.

Shame on Bioedge

It may be naïve to hope for better, but the world cannot afford sly pandering to lying propaganda. Failures of epistemic integrity have real practical consequences, and nowhere is this more obvious than in the middle east. Consider this:

The Independent Safeguarding Authority

10.10.2009 Anyone who wishes to work with children (or vulnerable people), including even a parent who wishes to help out in the school their child attends, is required to undergo vetting by the Independent Safeguarding Authority. The politicians responsible say that this will protect children from paedophiles.  
Philip Pullman (children’s book author) has refused to be vetted because “It is insulting and I think unnecessary, and I refuse to be complicit in any scheme that assumes my guilt.” As a result he will be banned from reading his books to children in schools. http://www.telegraph.co.uk/culture/books/booknews/5834646/Philip-Pullman-refuses-to-undergo-insulting-child-safety-check.html. The Children’s Laureate thinks that ‘the scheme [is] "governmental idiocy" which [will] drive a wedge between children and adults’. Arguably, then, believing it right to vet the enormous number of people that will be vetted (11.3 million by November 2010) is corrupting of the relations between adults and children, and is in part a manifestation of something poisonous in our attitude to adults. So there is a broad question over whether the ISA, simply through existing, has bad consequences and  is unjustly disrespectful. That is not what I want to discuss. I want to consider only the issue of the epistemic duty of the politicians who have created it and of the authority itself.

Economic uncertainty and epistemic humility

In the last six months I have heard that the current economic crisis proves that free market capitalism is a failure. I have also heard that it proves that government intervention is responsible for market booms and busts. I have read that the causes of the current crisis are greed, irrationality, easy money, low interest rates, perverse incentives, complex financial instruments, subprime mortgages, people believing that house prices would always rise, people insisting that houses must be made affordable,  the US congress laws that force banks to provide a certain percentage of subprime mortgages, the capital ratio requirements on banks being less for subprime mortgage backed securities than for prime mortgages, the distortion of mortgage lending by government sponsored entities (Freddie Mac and Fannie May), the lack of an exchange for credit default swaps creating un-noticed systemic counterparty risk, mark to market valuation of bank assets, too little government regulation, too much government  regulation, the government scaring us, the government not scaring us enough,  the lack of a bail out (stock market falls) , the delay of a bail out (stock market continues to fall), and the bail out (stock market carries on down).

Why am I talking about this? Because these circumstances are precisely the kind in which we in general and experts in particular indulge in a certain kind of epistemic irresponsibility: over-confidence in belief. When the stakes are high and circumstances highly uncertain it appears that we can hardly bear to conform our belief to the uncertainty. Paradoxically, uncertainty turns us to dogmatism.

Forensic Failure

Testimonial power is the power we have to determine the opinion of others by testifying. To testify is to make sincere assertions in such circumstances under which we are understood to be offering those assertions as to be worth relying upon. When things go well, we tell people what we know and they come to know it through our telling them.

Conspiracies against the laity and wishful thinking

Most duties are concerned with or grounded in  right actions. By contrast, an epistemic duty is a duty whose grounding object is belief or knowledge rather than action. My concern here is with a certain epistemic duty had by professionals and their professional organizations. Professionals present themselves in public as being in possession of special expertise and as taking on correlate special responsibilities. They require us to grant them special discretion on the promise of holding each other accountable through professional organizations, which organizations in turn present themselves in public as speaking for their profession.

Three arguments against turning the Large Hadron Collider on.

The physicists responses to worries about the risks posed by the LHC make it unclear whether they understand the moral issue. They may have the power, but they do not have the liberty to hazard the destruction of all present and future goodness. Nobody does.
Professor Frank Close of the University of Oxford has been quoted as saying that "The idea that it could cause the end of the world is ridiculous." (http://www.telegraph.co.uk/news/2008/04/06/wcern106.xml). Is it ridiculous because it is impossible, or because it is very unlikely? I don’t think he knows it is impossible, and being very unlikely is not sufficient to dismiss the risk. Yes, it’s very unlikely, but being very unlikely is not remotely unlikely enough, as, I think, these three arguments demonstrate.

My future self or myself in the future

In discussing issues such as, for example, whether prudential reasons can be accounted for in terms of desire based reasons, we sometimes contrast our present self with our future self. It's possible that some arguments turn on whether my present and future selves are distinct or whether talk of these selves is just a misleading way of speaking of me now and in the future. 4 dimensionalism (4D) accounts for persistence through time in terms of temporal parts, and if it is true then my future self is not identical to my present self, but both are temporal parts of me, whilst I am a space time worm that is the fusion of all my temporal parts (for short, a maximal space time worm). Jim Stone has recently offered a refutation of 4D in Analysis. Here is my condensed version of his argument:

Epistemic ethics

What is good and bad? What is virtue and vice? How should we live? These are the big questions of ethics. They are also deeply practical questions. The point is not simply to know the answers but to do what is right and to avoid what is wrong. Through action we pursue ends, manifest character and live life. Action is the nexus of ethical concern. Agents are the authors of action and are also the objects of ethical evaluation. The ethical standing of an agent bears a complex relation to their actions, to how they were sensitive to the ethically relevant facts in coming to their actions and to their general inclinations to act. But agency and action also require believers and  belief. What is the ethical status of believers and  belief, as such? And what relation do these evaluations surrounding action and belief have to one another?

Normative Bayesianism and Disagreement

Normative Bayesianism says that you ought to believe as you would if you were an ideal Bayesian believer and so believing is what it is to believe rationally. An ideal Bayesian believer has (1) beliefs by having credences, where a credence is a degree of belief in a proposition; (2) has a Prior = a complete consistent set of credences (capitalized to avoid confusing priors = a person’s credences with Priors = a plurality of complete consistent sets of credences), that is to say, has a credence function from the sigma algebra of propositions into the reals such that the credence function is a measure that is a probability function; (3) changes his beliefs on the basis of the evidence he has acquired by updating his credence function by the use of Bayes’ theorem.