The Liberal Modus Ponens Versus The Republican Modus Tollens


In my previous post, “The Republican Modus Tollens“, I pointed out that arguments apparently having the valid form

(1) If P then Q
(2) Not-Q
(3) So Not-P

allow for serious irrationality when P represents a matter of well-confirmed scientific theory and Q represents a prescriptive policy preference or a tenet of religious faith. So, to use one of the examples from my previous post, we have arguments about climate change that seem to be guided by the following pattern of thought-

(1) If climate change is occurring, then we should regulate CO2.
(2) We shouldn’t regulate CO2.
(3) So climate change isn’t actually occurring.

Of course, probably no opponent of climate change has ever explicitly made just this argument. My point is that the arguments they do make are evidently motivated by some such pattern of thought. Representing the pattern this way makes clear that they are often reasonable enough to recognize that if climate change were occurring, then we (perhaps) should regulate CO2. The problem is that they also very strongly desire not to regulate CO2 (perhaps for quite defensible reasons, such as worrying about the economic effects of such regulation), and this very strong desire against a possible policy choice, along with the normally valid modus tollens pattern of thought, leads them irrationally to deny a well-confirmed theory. In order to do so, they must massively over-weigh evidence contrary to climate change, sometimes fantasize about global conspiracies of scientists, and so on. It is this last move – the irrational denial of a scientific theory – that indicates they are being guided, at bottom, by strongly held policy positions and this modus tollens pattern of thought, or something similar to it.

Psychological explanations for why people argue like this aside, I suggested that the main logical problem with such arguments is located in their conditional (‘If P, then Q’) premises. This problem arises whenever P describes a putative matter of fact and Q expresses a prescription of some sort (often signaled by the inclusion of ‘should’ or ‘ought’). In such cases, the conditional statement can be viewed in one of two ways. If we view it as the sort of statement that actually belongs in a modus tollens argument (what logicians call a ‘material conditional’), then it can be criticized as being false on purely logical grounds. Famously, ‘is’ does not materially imply ‘ought’ – descriptive language does not materially imply prescriptive language. That does not mean that facts are irrelevant to policy choices, of course. As I put it in my previous post, facts can certainly bear on policies; it’s just that they never logically necessitate policies. On the other hand, if we view the conditional premise as a mere recommendation, then it doesn’t belong in a modus tollens form of argument at all, the argument form is only superficially similar to modus tollens, and the conclusion does not validly follow from the premises.

Now, almost as famous as “‘is’ does not imply ‘ought’” is another philosophical saying: “One person’s modus tollens is another person’s modus ponens“. Modus ponens is, like modus tollens, a valid form of argument that starts from a conditional premise. But in its second premise, instead of denying the conditional’s consequent (the statement that follows ‘then’), it affirms its antecedent (the statement that follows the ‘if’), and instead of deducing the conditional’s denied antecedent, it deduces its affirmed consequent. This sounds a lot more complicated than it is, as this sketch of the form shows-

(1) If P then Q
(2) P
(3) So Q

Starting from the conditional premise in the previous argument, we arrive at an argument that is commonly asserted by liberals-

(1) If climate change is occurring, then we should regulate CO2.
(2) Climate change is occurring.
(3) So we should regulate CO2.

A conservative upset with my prior post might try to turn the tables, observing that if the conditional premise is a problem in the modus tollens argument, then it is equally a problem in this modus ponens argument. I would reply that yes indeed, it is a problem, but not quite equally one. This is because in the cases that concern us, the antecedent is descriptive and the consequent is prescriptive, rather than the other way around. It is still true that the conditional statement is either false or not a material conditional (because it is a mere recommendation). But the difference is that when conservatives deny the antecedent because they deny the consequent, they are allowing their policy preferences to influence their view of the facts. On the other hand, when liberals affirm the consequent because they affirm the antecedent, they are merely allowing their view of the facts to influence their policy choice: precisely the rational thing to do. Even if both arguments are unsound or invalid from a purely logical viewpoint, in these cases the modus tollens sort of argument is irrational in a way that the modus ponens sort of argument is not.

Couldn’t the Republican arguments be expressed in a modus ponens form? Certainly. For instance-

(1) If climate change is not occurring, then we should not regulate CO2.
(2) Climate change is not occurring.
(3) So we should not regulate CO2.

The problem is that this way of representing their pattern of thought leaves the conspiracy theories and evidential biases that they rely upon to justify premise (2) totally unexplained. The same can be said for the other two arguments I discussed in the last post, in which premise (2) (of the modus ponens versions) would deny evolution and the safety of the HPV vaccine, respectively. Admittedly, some who deny evolution sometimes do so by promoting the notion of intelligent design, but the arguments for intelligent design are at least as weak as the arguments for the denial of climate change. The modus tollens representations help to explain why Republicans make such arguments (namely, because they are passionately against certain policies that they think might follow from acceptance of the facts); the modus ponens ones don’t.

By the way, some readers might have noticed an asymmetry in the title of this post versus that of the previous post: here I used ‘liberal’ instead of ‘Democratic’, whereas there I used ‘Republican’ instead of ‘conservative’. That is because, if the behavior of the House of Representatives and the current crop of Republican presidential candidates is any indication, the Republican party really has morphed into a purely conservative party. For better or for worse, thanks at least to the “blue dog” contingent, the Democratic party has not yet made a similar transformation into a purely liberal party.

Finally, it’s perhaps worth emphasizing that although the sort of irrationality I’ve sketched out above currently seems more common on the Right than on the Left, liberals are certainly not immune to it. The more passionately one holds a policy position, the more likely one is to fall into this style of thinking, and liberals can be just as passionate as conservatives. The answer, of course, isn’t to be less passionate. It’s simply to be more mindful of how those passions might influence one’s thinking.

The Republican Modus Tollens


Republican leaders have become fond of denying well-supported facts in the last few years, including such well-confirmed phenomena as (at least partly human-induced) climate change, the proven safety of vaccines, and of course evolutionary theory. What seems to be guiding them, at least unconsciously, is (roughly) the following form of argument, known to logicians as modus tollens-

(1) If P then Q
(2) Not-Q
(3) So Not-P

This pattern of reasoning is technically valid. That is, if the premises are true, then the conclusion must be true. So criticizing any argument of this form typically involves arguing that at least one of the premises is false.

For instance, here’s the Republican modus tollens argument against climate change:

(1) If climate change is occurring, then we should regulate CO2.
(2) We shouldn’t regulate CO2.
(3) So climate change isn’t actually occurring.

Or, similarly, in the case of the vaccine Michele Bachmann doesn’t like:

(1) If the HPV vaccine is safe, then we should encourage its use.
(2) We shouldn’t encourage its use.
(3) So the HPV vaccine is not safe.

Or, finally:

(1) If evolutionary theory is true, then the biblical story of creation should be denied.
(2) The biblical story of creation should not be denied.
(3) So evolutionary theory is not true.

Notice that in each of these arguments, P is a matter of well-confirmed scientific theory (there are no absolutely proven theories, of course – scientific methodology rules out such dogmatic certainty), while Q is a matter of social or political policy (or, in the last argument, religious faith). This makes the conditional (“If…then…”) premises extremely problematic (even if you agree with them), because they too simplistically suggest that facts logically entail policies, rather than simply bear on them. Thanks to this oversimplification, the arguer may think that it is necessary to deny a well-supported fact in order to avoid implementing a policy or contradicting a tenet of faith. This is psychologically understandable, but irrational and unnecessary. Policy recommendations and tenets of faith can certainly be debated on their own practical (or theological) merits. We can also debate the degree to which particular facts should bear on particular policies. But factual statements should stand or fall according to the evidence for or against them, not according to the policies to which they might lead or the theological issues they may raise.

For instance, at the risk of incurring some cognitive dissonance, Republicans could certainly continue to oppose regulating CO2 while accepting that climate change is occurring. After all, they could argue that despite the negative environmental effects of climate change, the negative economic effects of regulating CO2 would be even worse. This might well be false, but asserting it would not be as irrational as denying climate change merely for economic policy reasons. The same sort of criticism applies to the second argument. There is no need to deny a vaccine’s proven safety record merely because you want to discourage its use for, say, moral reasons. Let your moral argument stand on its own, and let the facts stand on their own. As for the third argument, many Christian theologians – both Catholic and Protestant – deny the first premise, since they argue that the book of Genesis was never meant to be a scientific description of how people came to exist. Atheists and agnostics might prefer to deny the second premise, but what is clear is that the evidence for evolution should stand (or fall) on its own.

What is truly disturbing is that so many Republican presidential candidates don’t seem to understand such obvious points, or, if they do, ignore them for the sake of influencing the gullible.

Wealth Distribution, Part II


Paul Solmon’s excellent PBS News Hour series on the economy continued this week, featuring – in a remarkable display of intellectual fairness – Robert Lerman’s objection to Solmon’s previous report on the increasingly huge inequality of wealth distribution in the United States (which I blogged on here). Solmon had originally described the situation using the statistics represented in this chart-

Lerman objects that when social security and medicare are included in the comparison, the inequality is not quite so disturbing-

Several commenters at the News Hour site point out that medicare and social security are not really the equivalent of other sorts of wealth in that they are not fungible, nor are they anything but financial burdens prior to one’s reaching retirement age. But putting those qualms aside, it’s worth pointing out that if entitlements really do have the effect of mitigating an otherwise (presumably) unfair wealth distribution, that’s all the more reason to save the programs from Republican attempts at dismantlement. In principle, I’m not against allowing individuals to “opt in” to riskier private retirement accounts, which might help to equalize wealth (and wealth-fungibility prior to retirement, if the law allows), as long as the “public option” could be retained in its current form for those who want it. But simple math suggests that with fewer people paying into the public option, the difference would have to be made up somehow… and what better way to make up the difference than by lifting the cap on the amount of income subject to payroll taxes, as well as by taxing super-wealth at higher rates,thereby further mitigating the wealth gap?

Lerman argues that at some point extreme wealth does not make a significant difference to quality of life. The capacity for pleasure is, after all, finite. Yes, the super-rich can drive a Ferrari while the rest of us drive Toyotas, but a car is basically a car, a palatial house is ultimately just a house (and, even if you own several, you can’t live in more than one at a time). I think that this might well be true, and that focusing on it may help to mitigate the resentment so many people are feeling these days. But, by the same token, doesn’t it help to bolster the argument that raising someone’s standard of living to a merely decent level by taxing someone else’s super-wealth at a slightly higher rate is morally defensible – maybe even morally required?

Here’s the entire thought-provoking segment-

Watch the full episode. See more PBS NewsHour.

Voter Fraud versus Voter Suppression


Rolling Stone has fairly comprehensive story this month concerning an apparently coordinated Republican effort to suppress Democratic voter turnout in 2012, debunking the rather transparent ruse that the purpose of the voter ID laws they are passing is simply to prevent voter fraud. As Ari Berman writes in his article entitled “The GOP War on Voting”-

A major probe by the Justice Department between 2002 and 2007 failed to prosecute a single person for going to the polls and impersonating an eligible voter, which the anti-fraud laws are supposedly designed to stop. Out of the 300 million votes cast in that period, federal prosecutors convicted only 86 people for voter fraud – and many of the cases involved immigrants and former felons who were simply unaware of their ineligibility. A much-hyped investigation in Wisconsin, meanwhile, led to the prosecution of only .0007 percent of the local electorate for alleged voter fraud. “Our democracy is under siege from an enemy so small it could be hiding anywhere,” joked Stephen Colbert. A 2007 report by the Brennan Center for Justice, a leading advocate for voting rights at the New York University School of Law, quantified the problem in stark terms. “It is more likely that an individual will be struck by lightning,” the report calculated, “than that he will impersonate another voter at the polls.”

Kathleen Dunn did an eye-opening interview with Berman yesterday on her show, which you can listen to here.

Of Ponzi Schemes And Social Security


According to Politifact, the candidates’ statements at yesterday’s Tea Party/CNN sponsored Republican Presidential debate contained a surprising number of inaccuracies (even given the low expectations most people have of such events). But perhaps the most egregious, in my view, is Rick Perry’s claim that Social Security is a “Ponzi scheme”. Politifact rates this claim as simply false. Here’s why-

So how valid is the comparison?

Mitchell Zuckoff, a Boston University journalism professor who has written a book on Ponzi, noted three critical dissimilarities between Social Security and a Ponzi scheme, which by definition is both fraudulent and unsustainable.

“First, in the case of Social Security, no one is being misled,” Zuckoff wrote in a January 2009 article in Fortune. “…Social Security is exactly what it claims to be: A mandatory transfer payment system under which current workers are taxed on their incomes to pay benefits, with no promises of huge returns.”

Second, he wrote, “A Ponzi scheme is unsustainable because the number of potential investors is eventually exhausted. That’s when the last people to participate are out of luck; the music stops and there’s nowhere to sit. It’s true that Social Security faces a huge burden — and a significant, long-term financing problem — in light of retiring Baby Boomers. … But Social Security can be, and has been, tweaked and modified to reflect changes in the size of the taxpaying workforce and the number of beneficiaries. It would take great political will, but the government could change benefit formulas or take other steps, like increasing taxes, to keep the system from failing.”

Third, Zuckoff wrote, “Social Security is morally the polar opposite of a Ponzi scheme… At the height of the Great Depression, our society (see “Social”) resolved to create a safety net (see “Security”) in the form of a social insurance policy that would pay modest benefits to retirees, the disabled and the survivors of deceased workers. By design, that means a certain amount of wealth transfer, with richer workers subsidizing poorer ones. That might rankle, but it’s not fraud… None of this is to suggest that Social Security is a perfect system or that there aren’t sizeable problems facing the incoming administration and Congress. But it’s not a Ponzi scheme. And Ponzi himself, who died in a hospital charity ward with only enough money for his burial, would never have recognized it as his own.”

We agree with Zuckoff’s interpretation. We rated Perry’s November 2010 comparison of Social Security and Ponzi schemes False, and we stand by that ruling. The comparison still deserves a rating of False.

Putting aside the Ponzi scheme charge, the fact that Social Security could be saved in perpetuity simply by raising the cap on the amount of wages subject to the payroll tax (currently set at $106,800), along with a modest, phased in increase of a year or two in the age at which one can receive full benefits, puts the lie to the often-heard claim that young people should not believe that benefits will be available to them. The simple truth is that such an outcome is likely to occur only if young people come to believe the claim and act to end the program, making it a self-fulfilling prophecy.

There may be principled grounds on which to be against Social Security, but basing opposition to the program on the fantasy that it cannot be saved is not one of them.

Music, Silence, and Miles Davis


I think the perfect music is probably silence and, as musicians, all [we] really do is create a rather beautiful and ornate frame for that perfection that is… silence. And some of my favorite artists really use silence very carefully and very artistically. Miles Davis, for example, knew the value and the measure of not playing. So what he didn’t play was as eloquent as what he did play.


You can catch the interview (on Charlie Rose) from which this quote was taken here.

And speaking of Miles Davis, here’s part of a performance in 1963, with his incredible quintet featuring pianist Herbie Hancock, saxophonist Wayne Shorter, bassist Ron Carter, and drummer Tony Williams (with whom I was lucky enough to work for a few weeks in 1976).

Kathleen Parker States The Obvious Well


Sometimes just stating the obvious with clarity is an accomplishment in our present media. Parker hits the nail on the head when she writes the following in an editorial about Texas Governor Rick Perry-

That we are yet again debating evolutionary theory and Earth’s origins — and that candidates now have to declare where they stand on established science — should be a signal that we are slip-sliding toward governance by emotion rather than reason. But it’s important to understand what’s undergirding the debate. It has little to do with a given candidate’s policy and everything to do with whether he or she believes in God.

If we are descended of some blend of apes, then we can’t have been created in God’s image. If we establish Earth’s age at 4.5 billion years, then we contradict the biblical view that God created the world just 6,500 years ago. And finally, if we say that climate change is partly the result of man’s actions, then God can’t be the One who punishes man’s sins with floods, droughts, earthquakes and hurricanes. If He wants the climate to change, then He will so ordain, and we’ll pray more.

Perry knows he has to make clear that God is his wingman. And this conviction seems not only to be sincere, but also to be relatively noncontroversial in the GOP’s church — and perhaps beyond. He understands that his base cares more the president is clear on his ranking in the planetary order than whether he can schmooze with European leaders or, heaven forbid, the media. And this is why Perry could easily steal the nomination from Romney.

And also why he probably can’t win a national election, in which large swaths of the electorate would prefer their president keep his religion close and be respectful of knowledge that has evolved from thousands of years of human struggle against superstition and the kind of literal-mindedness that leads straight to the dark ages.

Faith and reason are not mutually exclusive, but Perry makes you think they are.

And if you aren’t taken aback by Perry’s anti-science views, consider that he seems closely allied with leaders of the New Apostolic Reformation, a fundamentalist Christian group that advocates “spiritual warfare” in order to establish a totalitarian “dominion” over all aspects of society, as recently reported on NPR’s Fresh Air.