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Ravens clue to greater security

If, as Carl Hempel pointed out, the statement “all ravens are black” can yield the further insight that “all non-black objects are non-ravens,” then philosophy is useful to computer science. At least that’s the view of a number of computer scientists, led by Mexican Fernando Esponda of Yale. They are using such negative representations to create a negative database as a way of protecting sensitive data. Esponda told TPM that the connection with Hempel came to him when he was taking a philosophy of science class for fun. “What struck me was first that he had shown that a statement such as ‘All ravens are black’ is logically equivalent to ‘All non-black objects are non-ravens,’ but more so the apparent paradox that the existence of a yellow pencil can be taken as evidence for the original statement as well as for the contradictory ‘All

ravens are white’ (all non-white objects are non-ravens). In my Portia grant funded research I have been dealing only with finite sets, so Hempel translates as ‘All ravens in this zoo are black’ (‘All non-ravens in this zoo are non-black’) and its foe ‘All ravens in this zoo are white’ (all non-ravens in this zoo are non-white). In this scenario, conducting a parade of all the animals in the zoo will prove true one of the statements (or prove them both false); however, before that moment, seeing a pink flamingo coming down main street does indeed lend credence to both statements. Seeing the pink flamingo reduces the size of the observed zoo and consequently the perceived probability of seeing a brown raven. “This property, the Hempel’s paradox property, has an interesting potential for security since it is only when you have seen all the evidence that you can be certain which statement (data item) is true (hidden).” Esponda explained that the negative survey uses the same notion but in a reverse manner: instead of as a means to conceal information it’s used as a means to collect it privately, so that a survey can

The Philosophers' Magazine /4th quarter 2006

learn certain statistical properties of a population without associating specific data points to specific individuals. This is useful in surveys that ask for sensitive data, such as exit polls: the secret ballot is a cornerstone of properly functioning democracy, but at the same time exit polls are considered useful. Some voters may cherish the secrecy of their vote less than others and be happy to declare their choice to pollsters, but, Esponda explained, “this skews the sample towards that kind of personality, which may always vote for the same party. In a system where there are more than two parties an exit-poller can simply ask each participant to randomly disclose the name of one of the candidates she did not vote for. With this, an estimate of how people voted is possible. Also, think of any survey that requires disclosing potentially stigmatising information like the number of abortions that someone has had or how much money people make. As long as the questionnaire is multiple option with more than two options, this technique can be applied to promote participation.” So yet again the raven is a benefactor of humanity. reporter/11

media watch

philosophy and philosophers in the mass media

Aggression and massacre are legitimate causes of war...But the existence of regimes capable of aggression and massacre requires a different response. Michael Walzer, Dissent, Summer 2006

The outrage of so many outraged people outrages me. … Why do the 200,000 slaughtered Muslims of Darfur not arouse even half a quarter of the fury caused by 200-times fewer dead in Lebanon? André Glucksmann, Sign and Sight, August 10

The distinction between the state of war and peace is blurred. We are entering a time in which a state of peace itself can be at the same time a state of emergency. Slavoj Žižek, the Guardian, September 11

US foreign policy over the past few years has been driven by a mix of Christian and Enlightenment fundamentalism. John Gray, the New Statesman, July 31

I think it’s an oppressive idea that God is always looking into your soul at every moment of the day and weighing you up. I found it was liberating to not have that oppressive, Big Brother surveillance from God all the time. Colin McGinn, PBS, June 2006

We must preserve our freedom to deny the existence of God and to criticise the teachings of Jesus, Moses, Muhammad, and Buddha, as reported in texts that billions of people regard as sacred. Since it is sometimes necessary to use a little humour to prick the membrane of sanctimonious piety that frequently surrounds religious teachings, freedom of expression must include the freedom to ridicule as well. Peter Singer, Free Inquiry, JuneJuly 2006

It is from a posture of irony that every real negotiation, every offer of peace, every acceptance of the other, begins. Roger Scruton, the Wall Street Journal, August 20

The Nazis can disrupt the streets of Skokie, but those who disrupt Rumsfeld’s message will be carried away with the hands of secret service agents clamped over their mouths. Jeremy Waldron, the London Review of Books, July 20

One of the problems of what is happening in Britain today is that one identity, the religious identity, has been taken to represent almost everything. Amartya Sen, the Daily Telegraph, July 27

How could we possibly hope that our universities might become world class if we did not think that they were elitist? Mary Warnock, the Observer, August 20

Our opinions are fallible, and judgement is far from perfect, but the remedy for any imperfect use of it lies in using more of it. Simon Blackburn, the Financial Times, July 28

I’m not one to play the dirty little game of counting corpses. But why shouldn’t what is due to some also be due to others? Bernard-Henri Lévy, the New York Times, August 6

One may learn how to think about the arguments of Plato and Aristotle from someone whom one might not like to have as a friend. Martha Nussbaum, the TLS, July 12

Although a good God regrets our suffering, his greatest concern is surely that each of us shall show patience, sympathy and generosity and, thereby, form a holy character Some people badly need to be ill for their own sake, and some people badly need to be ill to provide important choices for others. Richard Swinburne, Science and Theology News, June 27

The Philosophers' Magazine /4th quarter 2006