Man is a rational animal who always loses his temper when called upon to act in accordance with the dictates of rationality. - Orson Wells It's no secret that Hamas desperately wants the June 19 temporary truce to last for as long as possible. An Arab source told me that the Islamist group has been under severe pressure - not so much, he claims, from the IDF as from distressed Gazans who need a respite from Israeli and international sanctions, which have made their lives absolute misery. Of course, Hamas also wants time, unmolested by the IDF, to import concrete which it will use to expand its network of tunnels and bunkers (hence the need for opening the overland passages from Israel). It also wants to smuggle in more powerful explosives, anti-aircraft and anti-tank missiles, stock up on shekels and send promising operatives for specialized training abroad. With all these incentives, how do you explain the fact that the Palestinians almost immediately violated the truce by firing rockets into Israel? Marcus Sheff, executive director of the Israel Project, quips that extremist Palestinian factions have "Terrorist Tourette's" - they can't behave rationally because they suffer from an unaccountable, violent "tic" that compels self-destructive outbursts. Either the Palestinians are behaving irrationally, or we're misinterpreting what they're doing as irrational, or we are the ones who are being irrational and don't know it. Or - perhaps even more problematic - rationality isn't all it's cracked up to be, and human beings can't but behave irrationally at times. WHILE NO one sets out to behave foolishly and we all think we're sensible and that our reasoning is logical, the possibility that we're kidding ourselves about how rational we are comes up repeatedly. Take the latest research published in the journal Neuron and reported in last week's Economist, in which a team led by Brian Knutson and G. Elliott Wimmer hypothesize that people have a tendency to over-value items they own to an irrational extent. This also helps explain why some very high-IQ people I know are chronically disorganized and can't part with clutter. Modern offices (and small Israeli apartments) demand tidiness, but evolution has imprinted our brains with an even stronger need to horde. Primitive man, it seems, can't easily part with his tangible possessions. Nor can we. IF YOU want the case for rationality, let me recommend The Last Lecture by Randy Pausch, the young computer science professor at Carnegie Mellon who was diagnosed with pancreatic cancer and told he had only months to live. Pausch's book is based on a "last lecture" he gave to his students; it has been viewed by many others via the Internet. It's also meant as an expression of love to his wife and a way to pass on his values to his three small children. He tells them: "You can't control the cards you're dealt, just how you play the hand." In these heartrending but in no way maudlin ruminations, Pausch implicitly addresses the question Aristotle posed 2,000 years ago: What is the best, the happiest, the most meaningful sort of life worth living? His answer: a life that combines emotional intelligence with rationality. THE NEXUS between rationality and death also came up this week, when the Israeli cabinet decided to trade a demonic terrorist for the remains of two fallen IDF soldiers. To my mind, it was not merely a wrong but an irrational decision, since it only strengthens our enemies' dangerous conviction that if they stand firm, we will always cave. And yet it was taken by an overwhelming majority of ministers amid wide popular and media support. Plainly, we all define "rational" differently. TAKE ANOTHER, more prosaic decision by Cabinet Secretary Ovad Yehezkel - about bottled mineral water - that seems, on the surface, to be perfectly rational. Telling ministers that a cubic meter of mineral water costs 1,000 times more than tap water, Yehezkel wants ministries to stop ordering mineral water and install water purifiers. As my colleague Herb Kenion put it: "He said this to ministers who, for the first time in recent memory, were sitting around a cabinet table bereft of the little blue plastic bottles of water." Now I use tap water for my Shabbat urn and bottled water during the rest of the week - and, believe me, you can taste the difference. Thus there is a rational case to be made for bottled water: It tastes better. And I can afford the indulgence, so my decision to use mineral water is therefore rational. But whether Yehezkel's decision is rational depends on the cost-benefit ratio. Are machines that purify and chill (and often also boil) water really cheaper than water in bottles? The government will have to purchase or rent the new equipment, invite bids for its maintenance, and bring in plumbers to draw tap water pipes to innumerable locations in government buildings throughout the country. These costs are worth looking into. It may be perfectly sensible for Americans, on the other hand, to question the rationality of spending $11 billion a year on bottled water. Manufacturing all those plastic bottles leaves one big carbon foot-print; producing them uses up the equivalent of an amazing 17 million barrels of oil. While tap water may contain pollutants (not to mention microscopic creatures, as ultra-Orthodox Jews in NYC have discovered), the quality of bottled water is often only loosely regulated. Reasoning can therefore take you only so far: It may well be that there is no rational answer to the tap vs mineral water debate. MICHAEL CHABON'S The Yiddish Policemen's Union, which I have just read, also grapples with the rationality issue. Though no great Zionist, Chabon is a talented and imaginative storyteller. Toward the end of the book he places an epiphany, of sorts, in the mind of the main character, detective Meyer Landsman: "All at once he feels weary of ganefs and prophets, guns and sacrifices and the infinite gangster weight of God. He's tired of hearing about the promised land and the inevitable bloodshed required for its redemption. 'I don't care what is written. I don't care what supposedly got promised to some sandal-wearing idiot whose claim to fame is that he was ready to cut his own son's throat for the sake of a hare-brained idea. I don't care about red heifers and patriarchs and locusts. A bunch of old bones in the sand. My homeland is my hat. It's my ex-wife's tote bag.'" All very imaginative, but the case is strong that - far from being a "sandal-wearing idiot," Abraham handled his situation with perfect rationality, an argument made by NYU Prof. Steven J. Brams in his book Biblical Games. Brams claims that "rational interpretations of biblical actions are no more farfetched than 'faith' interpretations." And in his game theory construct, "the more sophisticated the rationality calculations biblical characters make, the less need for them to have blind faith in God to achieve their goals." Anyway, and without away giving too much of the plot, the dilemma Chabon's Jews face is in large measure not of their own making. It may be rational for Meyer Landsmanan, as a lone Jew, to opt out, but history has amply demonstrated that as a people, we cannot cast off our scripted role - rationality be dammed.