Post hoc ergo propter hoc

March 31, 2012 3:24 pm


The Economist hosted a debate between security expert Bruce Schneier and former TSA-administrator Kip Hawley on the topic of whether the changes to airport security since 9/11 have done more harm than good.

It was well done and consisted of opening statements, rebuttals, and closing statements from each participant.

Hawley's opening statement begins with:

More than 6 billion consecutive safe arrivals of airline passengers since the attacks on America on September 11th 2001 mean that whatever the annoying and seemingly obtuse airport-security measures may have been, they have been ultimately successful.

He continues on and on using the reasoning that because no airplanes have been successfully attacked it means the TSA has been effective and therefore worth its inconvenience, cost, and violation of civil rights.

This is a clear-cut case of post hoc ergo propter hoc reasoning.  He presents no further evidence other than first the TSA was created and second no successful attacks have occurred as proof that the TSA is successful.

Post hoc ergo propter hoc can be phrased as follows: First A occurred, then B occurred, therefore A caused B.  This, however, is frequently not true and is not valid reasoning without further evidence better tying together the events of A and B.

Using post hoc ergo propter hoc reasoning as the sole basis of maintaining the current absurdity of the TSA is unacceptable.

But let's rephrase the relationship and re-examine the reasoning.  Let's phrase the relationship like this:

If the TSA is effective then there will be no successful attacks on U.S. airplanes

Now let's include the knowledge that no successful attacks have occurred.  What can we say about the TSA's efficacy?

Interestingly enough, nothing.  If the if-then relationship is true, knowing the "then" clause is true tells us nothing about the "if" clause.

Logically, if-then statements can be rewritten.  "If A then B" is equivalent to "B or not A."  Using an example:  "If it is raining then the ground is wet" is equivalent to "The ground is wet or it is not raining."

The re-writing makes it easy to see that when we know the ground is wet we don't actually learn anything about whether it is raining or not.  It might be raining, and the wet ground provides evidence for that hypothesis, but the ground may be wet because a lawn sprinkler is running, or someone spilled a cup of water.  We don't know why the ground is wet, only that it is.

So let's rewrite our proposed relationship between the TSA and airplane safety:

There will be no successful attacks on U.S. airplanes or the TSA is not effective.

Knowing that there have been no successful attacks tells us nothing about whether the TSA is effective or not.

This is an incredibly important piece of formal logic to understand because it is almost always misused in common practice.

So the real relationship that Hawley is providing evidence to argue is this:

If there are no successful attacks on U.S. airplanes then the TSA is effective.

But this statement doesn't mean what Hawley wants it to mean.  Given that there are no successful attacks on U.S. airplanes does mean that the TSA achieved its operational goal, but it does not tell us anything about whether the TSA's actions contributed to that result or not because the causation is backwards.

It is equivalent to saying: "If I got an A on the test then I learned the material."  Which is not necessarily true (you may have cheated or made lucky guesses).  The correct causation should be, "If I learned the material then I will have gotten an A on the test."

In order for the test->learned form to tell us something meaningful about the consequent (the "then" part) we need additional criteria: "If I got an A on the test, and I did not cheat, and I did not make lucky guesses then I learned the material."

[Updated 4/14 with more obvious example]
Another example would be to say I have a magic wand that causes things to fall to the ground when you let go of them.  I'm holding the wand, you let go of something, it falls to the ground.  So I posit, "If the object falls to the ground, then my wand works."  Knowing that the object falls to the ground doesn't really tell you anything about whether my magic wand had anything to do with it.  The stated purpose of the wand was achieved, but it had nothing to do with the wand.

The point being that in this reverse-causation form we have to account for all possible causes in the antecedent (the "if" part) in order to arrive at the consequent--an impossible task given the number of things that are unknowable regarding airplane security.

There may be no successful attacks on U.S. airplanes for many reasons and we would need to account for all of them before declaring the TSA effective.  A silly one is simply that there might be no U.S. airplanes (in which case there could be no attacks against them, successful or otherwise, regardless of the TSA's efficacy).

A serious reason could be that there is not anyone trying to attack.  And if we count the number of terrorists that the TSA has actually caught (zero), this is true.  If your argument is then that those who would attack were deterred from even trying, then the burden is on you to provide evidence that this has occurred.

My position remains that if terrorists were intent on blowing something up and decided that an airplane was too difficult they would not just give up and go home.  If the TSA is deterring terrorists from attacking airplanes then those same terrorists would be blowing up grocery stores, malls, schools, dams, airport security lines (like the terrorist attack in Russia in 2011), or any of thousands of other completely unprotected targets.

Bruce Schneier argued for the responsible action: Disassemble the TSA, return airport security to pre-9/11 levels, and divert the TSA's budget to intelligence gathering, law enforcement, and emergency response.

Following this plan would provide greater protection for all targets with no meaningful reduction to the security of airplanes.  And, as a bonus, you would waste less time in airport security lines, have fewer Constitutional rights violated when traveling, and your ticket would cost less.

Congressional Herp Derp

March 27, 2012 7:56 am

On March 26, 2012, the House Committee on Oversight & Government Reform held a hearing titled "TSA Oversight Part III: Effective Security or Security Theater?"

Leading security expert, TSA critic, and coiner of the phrase "security theater," Bruce Schneier had been formally invited by the committee to provide testimony.  On Friday, Schneier was informed that his invitation had been revoked by request of the TSA.  Supposedly the TSA objected to his testimony on grounds that he is currently involved in a legal suit against the TSA and this somehow disqualifies his testimony.

Well, surely wanting a fair and reasoned hearing the committee found some other security expert to provide testimony, right?


Here is the entire witness list of the day's hearing:

Assistant Administrator for Security Operations
Transportation Security Administration
Assistant Administrator for Intelligence and Analysis
Transportation Security Administration
Director, Homeland Security Program
U.S. Government Accountability Office
Assistant Commandant for Marine Safety, Security & Stewardship, U.S. Coast Guard
The fist three witnesses having direct interest in not only maintaining the status quo but expanding the program.  And the fourth not having any obvious reason to be involved in a hearing on airline security.
Not one witness allowed to testify in a manner that might expose the ineptness of the program or support the protection of civil rights over theater.

Good Business

March 26, 2012 4:56 pm

I recently started reading a series published by BenBella. I discovered that the third book in the series (Lady of Mercy by Michelle Sagara West) was missing thirty pages! I was confused by the jump in narrative until I noticed the page numbers. So, that was pretty weird. I emailed the publisher, though, explaining the situation and got an email back the next business day apologizing and asking where a new copy could be sent. I got my new book in the mail today, so I'm pretty pleased with how this turned out. I wasn't sure I would actually get a response at all from them, but I got a very prompt one and a replacement. Very nice.

The Death of "Due Process of Law"

March 23, 2012 10:56 am

On September 30, 2011, on orders from President Obama, U.S. citizen Anwar al-Awlaki was assassinated in Yemen.  At the time, many people expressed concern over the assassination of a U.S. citizen--the assassination of someone born in New Mexico and educated in Colorado (B.S.), California (M.A.), and Washington D.C (incomplete Ph.D.).  And many people defended the action, justifying it on the basis that he was aiding and abetting terrorists.

al-Awlaki had never been tried or convicted of any crime in any U.S. court.

Up until this point, in the United States we followed the law set forth in the Constitution.  The Fifth Amendment states:

No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.

The key phrase I'd like to emphasize is, "No person shall be...deprived of life...without due process of law."

"Due process of law" is a critical concept in the functioning of any society that claims to hold itself to the rule of law.  According to Wikipedia's article on the "Due Process Clause":

The Supreme Court of the United States interprets the Clauses as providing four protections: procedural due process (in civil and criminal proceedings), substantive due process, a prohibition against vague laws, and as the vehicle for the incorporation of the Bill of Rights.

And quoting from the article on "Substantive Due Process":

[Procedural due process] aims to protect individuals from the coercive power of government by ensuring that adjudication processes under valid laws are fair and impartial (e.g., the right to sufficient notice, the right to an impartial arbiter, the right to give testimony and admit relevant evidence at hearings, etc.).

[Substantive due process] aims to protect individuals against majoritarian policy enactments which exceed the limits of governmental authority—that is, courts find the majority's enactment is not law, and cannot be enforced as such, regardless of how fair the process of enforcement actually is.

On March 5, 2012 Attorney General Eric Holder gave a speech at Northwestern University Law School in Chicago.  In this speech he defended the administration's actions and discussed how they unilaterally redefined the meaning of "due process of law":

Some have argued that the President is required to get permission from a federal court before taking action against a United States citizen who is a senior operational leader of al Qaeda or associated forces. This is simply not accurate. 'Due process' and 'judicial process' are not one and the same, particularly when it comes to national security. The Constitution guarantees due process, not judicial process.

I don't know how anyone can reconcile his statements with the above discussion on the definition of "due process of law."

It appears to be the exact same type of word games that the Bush administration played in order to permanently incarcerate people at Guantanamo Bay without trials.  By simply calling them "enemy combatants" instead of "prisoners of war" or "criminals" they made a linguistic end-run around both the U.S. Constitution and the Geneva Conventions.  The same way that torture was illegally used by calling it "enhanced interrogation."

Using these kinds of language tricks one can get away with anything and the rule of law collapses.

I'm concerned for our future when our rights can simply be redefined away.

Have Mercy

March 15, 2012 7:21 pm

Recently, Heather has taken to screaming fits when we try to put her to sleep. 

Often, we can get her to sleep and then after anywhere from 0-30 minutes she'll wake up crying and then screaming and nothing seems to calm her down.  She acts likes she's just in horrible discomfort.  And this will continue for what feels like forever, but is usually more like up to 30 minutes.

Last night this went on and off for about 3.5 hours before she finally stayed asleep for a few hours.

We've tried all our normal soothing techniques as well as feeding her and administering Colic Calm.  There doesn't seem to be any strong correlation between any of these actions and her eventual calming down.

Usually, once it passes, she's in a really good mood like nothing ever happened.  And this change can happen in a matter of minutes.

Anyone have any bright ideas about what she could be so upset about?  Or magic ways to help soothe her?