<p>I guess you might already know this, but I wanted to add a little detail to the other answers for the sake of any layman who comes here and gets the wrong end of the stick.</p>

<h2>What is meant by rationality?</h2>

<p>It is important to begin by saying that when economics use the term rational they have in mind a fairly precise definition that does not perfectly coincide with the way the word is sometimes used colloquially:</p>

<blockquote>
  <p>We say that a decision maker is rational if</p>
  
  <ul>
  <li>s/he has preferences that are transitive and complete</li>
  <li>s/he acts in a manner consistent with optimization with respect to those preferences. </li>
  </ul>
</blockquote>

<p>On the first bullet: suppose some one has to make a decision. We say that they have transitive and complete preferences if (i) they are able to rank the alternatives among which they choose from "most preferred" to "least preferred", and (ii) that ranking is internally consistent.</p>

<p>On the second bullet: A person acts in an optimal manner given their preferences if they choose the alternative that is 'most preferred' among the set of all feasible alternatives.</p>

<h2>So are terrorists rational?</h2>

<p>As others have noted, the literal answer to the question is that we can't really (empirically) verify that terrorists are rational. This is because observing one rational decision does not rule-out the possibility that the individual concerned made an <em>irrational</em> decision at some point in the past (or that they will make an irrational decision in the future). The best we can manage is to look for behavior that violates the two conditions above and take observations of such violations to be evidence of irrationality.</p>

<p>But, to address the spirit of the question: just because voluntarilly committing suicide and murder in the name of your beliefs may <em>seem</em> irrational in the colloquial sense does not mean that it is necessarily so. Indeed, <strong>if a person has carefully considered the alternatives available to them and decided that the option they find most attractive is to conduct a suicide attack then this behaviour is entirely consistent with rationality.</strong></p>

<h2>Rational terrorism in context</h2>

<p>It is important to stress that there is no value judgement implicit in an eocnomist describing behaviour as rational. Just because something is rational behaviour does not mean that it is good or desirable or can be condoned. Rather, it just means that we think we have a systematic way of understanding why people might choose to behave in a certain way. Building a systematic understanding of a phenomenon is an important first step in deciding upon the best way to respond to it.</p>

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2015-12-09T16:10:41.120Z
2015-12-09T17:29:34.583Z
2015-12-09T17:29:34.583Z
Ubiquitous
<p>I don't think we have enough data on that matter. They would be irrational, for example, if transitivity of their preferences does not hold. How do we get their preferences? Through the axiom of revealed preferences (WARP). </p>

<p>We can never say whether someone is rational, we can only say whether someone is irrational (read: his actions are not rationalizable). That is, if we observe 10 decisions from a person, and they are not conflicting, this is not sufficient to say that he is rational. However, if they <em>do</em> conflict, it is sufficient information to say that he is irrational.</p>

<p>You phrased the question about individual terrorists, and not about the collective. Hence, to judge any single one, we would need to observe enough actions to judge his preferences, and see whether we fail to rationalize his actions under a preference ordering. And then, to repeat myself, I don't think we have enough data on that matter.</p>

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2015-12-09T16:41:13.733Z
Thanks @FooBar. If by saying that we don't have enough data you think about data on terrorist's priors and beliefs I definitely agree
emeryville
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2015-12-09T16:48:13.900Z
By sharing @RegressForward's point of view, I doubt we can say that someone is irrational (read his/her actions are not rationalizable) based on conflicting actions. It's "a failure to find a tractable utility function that adequately models their behavior." We definitely need more data on beliefs and priors.
emeryville
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2015-12-09T17:51:16.597Z
@emeryville Yes, your (RegressForward's) points are not that WARP does not hold, it's just that data necessary to find a violation of WARP is really hard, because even if someone apparently contradicts himself with two actions, maybe there's something about the background information (such as priors) that changed between those two events. Indeed, WARP is hard to apply outside of clean laboratory settings.
FooBar
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2016-02-16T01:27:05.507Z
@emeryville Interesting. May I add to the discussion? Theoretically, we have preference relations, definitions, and logical rules. In this abstract world, deductions can be made. However, are we not dealing with an empirical, or real world, matter? If so, this lends itself to casting the question into a Bayesian framework. For this reason, the question is probably, should I have degrees of confidence to believe that terrorists are rational? Uncertainty abound, it's conceivable that some terrorists are rational while others irrational. The answer may not be one of extremes (to excuse the pun).
Graeme Walsh
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2016-02-22T18:07:23.077Z
Thanks @GraemeWalsh. Interesting point! Do you have references "to casting the question into a Bayesian framework"?
emeryville
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2016-02-22T18:32:42.770Z
@emeryville Maybe that sounded more formal than I intended. I really just meant, "look at it from a Bayesian perspective". A decent reference is Leamer's Specification Searches book or Zellner's Intro to Bayesian Econometrics. Early chapters in both books have diagrams/flowcharts of a "Bayesian learning process". I basically figured, it would be interesting to ask/answer the question with reference to this particular kind of process in mind.
Graeme Walsh
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2016-02-22T19:09:47.983Z
Thanks @GraemeWalsh. It would be useful I guess to have these comments as an elaborated answer.
emeryville
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2015-12-09T09:58:37.150Z
2015-12-09T09:58:37.150Z
FooBar
<p><a href="http://economics.uwo.ca/people/faculty/wintrobe.html" rel="nofollow">Ron Wintrobe</a> has a book on <a href="http://www.cambridge.org/us/academic/subjects/economics/public-economics-and-public-policy/rational-extremism-political-economy-radicalism" rel="nofollow"><em>Rational Extremism</em></a>, which explains how behavior of terrorists, in particular suicide bombers may be "rationalized". He theorizes that the act of blowing up oneself is a form of corner solution to an optimization problem faced by terrorists. </p>

<p>Here's a preview of one of the chapters of the book: <a href="http://economics.ca/2005/papers/0708.pdf" rel="nofollow">http://economics.ca/2005/papers/0708.pdf</a></p>

CC BY-SA 3.0
2015-12-10T05:13:41.283Z
2015-12-10T05:13:41.283Z
Herr K.
<p>We can not prove terrorists are not rational.  We can only have a failure to find a tractable utility function that adequately models their behavior.  </p>

<p>On the practical side, one cannot see enough decisions from a person <em>ceteris paribus</em> to confirm much about their rationality. Too much happens over time, without observation, and in a noncontinuous manner. Perhaps we can acquire evidence that their actions have a degree of stochastic noise about them. Or that they do they do not fit model X, or we are omitting a variable Y.</p>

<p>On the theoretical side, for any set of behaviors, Z, one can name an array of utility functions f(Z) which would explain such behavior.  I say nothing optimistic about the <em>simplicity</em>, <em>verification</em>, or <em>stability</em>  of these utility functions, but they can be modeled nonetheless.  We can only eliminate a fraction of those f(Z)'s empirically. We are left with some f(Z)'s that could defend their rationality, it remains possible they are rational.</p>

<p>Absence of evidence is not evidence of absence.</p>

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2015-12-09T14:18:53.633Z
2015-12-09T18:13:07.780Z
2015-12-09T18:13:07.780Z
RegressForward
<p>Terrorists are definitely rational. Each one of them maximizes their utility by blowing themselves up. Their preferences and utilities are defined by their beliefs, of course, not the reality of the situation. Their <a href="https://en.wikipedia.org/wiki/Bounded_rationality" rel="nofollow">rationality is bounded</a>, because they may not know that their beliefs are false or misguided.</p>

<p>The open question is how bounded is the terrorists' rationality. There are plenty of works out there, which I admit I haven't read, but <a href="http://www.rand.org/pubs/commercial_books/CB386.html" rel="nofollow"><em>Inside Terrorism</em> by Bruce Hoffman</a> looks to be a very popular one.</p>

CC BY-SA 3.0
2015-12-09T13:06:05.037Z
As economists, I note that our hinges upon the idea that our subjects are rational... just with perverse utility functions. Note that you cannot prove otherwise, there is always a more complex utility function to model a behavior.
RegressForward
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2015-12-10T15:38:20.790Z
"*Terrorists are definitely rational*". What does that even mean: Is the concept of rationality defined based on properties of terrorists?
FooBar
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2015-12-09T08:41:25.600Z
2015-12-09T08:41:25.600Z
Arthur Tarasov
<blockquote>
  <p>Terrorism in general, and suicidal terrorism in particular, is
  popularly seen as “irrational,” but many economists and political
  scientists argue otherwise.</p>
</blockquote>

<p>This quote is from <a href="http://econfaculty.gmu.edu/bcaplan/pdfs/terrorism.pdf" rel="nofollow">Terrorism: The relevance of the rational choice model</a> by Bryan Caplan. This paper has been published in 2006 in Public Choice. In relation with the recent terrorist attacks in Paris (Nov. 15), is there any new (economic) development on the question of the rationality of terrorism?</p>

<p>Edit: the title is intentionally short but by saying “is X rational?" I definitely mean "Can X be rationalized?"</p>

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2015-12-09T07:36:55.757Z
Economics can't answer "is X rational?" That's the domain of psychology. Economics *can* answer "Can X be rationalised?"
410 gone
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2015-12-09T07:39:23.117Z
However, any good economist should be a decent psychologist :)
Thorst
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2015-12-09T07:40:52.513Z
@Lasse well that excludes just about everyone then.
410 gone
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2015-12-09T07:42:04.857Z
At least one guy got the Nobel Prize in economics "for having integrated insights from psychological research into economic science"...
emeryville
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2015-12-09T08:07:18.390Z
@emeryville Wouldn't that imply that any good psychologist can be a decent economist?
Giskard
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2015-12-09T18:16:54.710Z
@denesp I guess there is a "and a good mathematician/logician" part to it to ;)
VicAche
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2015-12-13T21:39:42.757Z
@EnergyNumbers psychology? myb philosophy?
BCLC
<microeconomics><reference-request><choice-theory>
Are terrorists rational?
emeryville
# Are terrorists rational?

(Asked by: username_0 on 2015-12-09)

> Terrorism in general, and suicidal terrorism in particular, is
> popularly seen as “irrational,” but many economists and political
> scientists argue otherwise.

This quote is from [Terrorism: The relevance of the rational choice model](http://econfaculty.gmu.edu/bcaplan/pdfs/terrorism.pdf) by Bryan Caplan. This paper has been published in 2006 in Public Choice. In relation with the recent terrorist attacks in Paris (Nov. 15), is there any new (economic) development on the question of the rationality of terrorism?

Edit: the title is intentionally short but by saying “is X rational?" I definitely mean "Can X be rationalized?"

**Tags:** microeconomics, reference-request, choice-theory
> **Comments:**
> **username_1**: Economics can't answer "is X rational?" That's the domain of psychology. Economics *can* answer "Can X be rationalised?"  
> **username_2**: However, any good economist should be a decent psychologist :)  
> **username_1**: @Lasse well that excludes just about everyone then.  
> **username_0**: At least one guy got the Nobel Prize in economics "for having integrated insights from psychological research into economic science"...  
> **username_3**: @emeryville Wouldn't that imply that any good psychologist can be a decent economist?  
> **username_4**: @denesp I guess there is a "and a good mathematician/logician" part to it to ;)  
> **username_5**: @EnergyNumbers psychology? myb philosophy?  

---

## 5 answers

### Answer by username_6 on 2015-12-09. Score: 11

I guess you might already know this, but I wanted to add a little detail to the other answers for the sake of any layman who comes here and gets the wrong end of the stick.

## What is meant by rationality?

It is important to begin by saying that when economics use the term rational they have in mind a fairly precise definition that does not perfectly coincide with the way the word is sometimes used colloquially:

> We say that a decision maker is rational if
>
> * s/he has preferences that are transitive and complete
> * s/he acts in a manner consistent with optimization with respect to those preferences.

On the first bullet: suppose some one has to make a decision. We say that they have transitive and complete preferences if (i) they are able to rank the alternatives among which they choose from "most preferred" to "least preferred", and (ii) that ranking is internally consistent.

On the second bullet: A person acts in an optimal manner given their preferences if they choose the alternative that is 'most preferred' among the set of all feasible alternatives.

## So are terrorists rational?

As others have noted, the literal answer to the question is that we can't really (empirically) verify that terrorists are rational. This is because observing one rational decision does not rule-out the possibility that the individual concerned made an *irrational* decision at some point in the past (or that they will make an irrational decision in the future). The best we can manage is to look for behavior that violates the two conditions above and take observations of such violations to be evidence of irrationality.

But, to address the spirit of the question: just because voluntarilly committing suicide and murder in the name of your beliefs may *seem* irrational in the colloquial sense does not mean that it is necessarily so. Indeed, **if a person has carefully considered the alternatives available to them and decided that the option they find most attractive is to conduct a suicide attack then this behaviour is entirely consistent with rationality.**

## Rational terrorism in context

It is important to stress that there is no value judgement implicit in an eocnomist describing behaviour as rational. Just because something is rational behaviour does not mean that it is good or desirable or can be condoned. Rather, it just means that we think we have a systematic way of understanding why people might choose to behave in a certain way. Building a systematic understanding of a phenomenon is an important first step in deciding upon the best way to respond to it.


---

### Answer by username_7 on 2015-12-09. Score: 4

I don't think we have enough data on that matter. They would be irrational, for example, if transitivity of their preferences does not hold. How do we get their preferences? Through the axiom of revealed preferences (WARP).

We can never say whether someone is rational, we can only say whether someone is irrational (read: his actions are not rationalizable). That is, if we observe 10 decisions from a person, and they are not conflicting, this is not sufficient to say that he is rational. However, if they *do* conflict, it is sufficient information to say that he is irrational.

You phrased the question about individual terrorists, and not about the collective. Hence, to judge any single one, we would need to observe enough actions to judge his preferences, and see whether we fail to rationalize his actions under a preference ordering. And then, to repeat myself, I don't think we have enough data on that matter.

> **Comments:**
> **username_0**: Thanks @FooBar. If by saying that we don't have enough data you think about data on terrorist's priors and beliefs I definitely agree  
> **username_0**: By sharing @RegressForward's point of view, I doubt we can say that someone is irrational (read his/her actions are not rationalizable) based on conflicting actions. It's "a failure to find a tractable utility function that adequately models their behavior." We definitely need more data on beliefs and priors.  
> **username_7**: @emeryville Yes, your (RegressForward's) points are not that WARP does not hold, it's just that data necessary to find a violation of WARP is really hard, because even if someone apparently contradicts himself with two actions, maybe there's something about the background information (such as priors) that changed between those two events. Indeed, WARP is hard to apply outside of clean laboratory settings.  
> **username_8**: @emeryville Interesting. May I add to the discussion? Theoretically, we have preference relations, definitions, and logical rules. In this abstract world, deductions can be made. However, are we not dealing with an empirical, or real world, matter? If so, this lends itself to casting the question into a Bayesian framework. For this reason, the question is probably, should I have degrees of confidence to believe that terrorists are rational? Uncertainty abound, it's conceivable that some terrorists are rational while others irrational. The answer may not be one of extremes (to excuse the pun).  
> **username_0**: Thanks @GraemeWalsh. Interesting point! Do you have references "to casting the question into a Bayesian framework"?  
> **username_8**: @emeryville Maybe that sounded more formal than I intended. I really just meant, "look at it from a Bayesian perspective". A decent reference is Leamer's Specification Searches book or Zellner's Intro to Bayesian Econometrics. Early chapters in both books have diagrams/flowcharts of a "Bayesian learning process". I basically figured, it would be interesting to ask/answer the question with reference to this particular kind of process in mind.  
> **username_0**: Thanks @GraemeWalsh. It would be useful I guess to have these comments as an elaborated answer.  

---

### Answer by username_9 on 2015-12-10. Score: 3

[Ron Wintrobe](http://economics.uwo.ca/people/faculty/wintrobe.html) has a book on [*Rational Extremism*](http://www.cambridge.org/us/academic/subjects/economics/public-economics-and-public-policy/rational-extremism-political-economy-radicalism), which explains how behavior of terrorists, in particular suicide bombers may be "rationalized". He theorizes that the act of blowing up oneself is a form of corner solution to an optimization problem faced by terrorists.

Here's a preview of one of the chapters of the book: <http://economics.ca/2005/papers/0708.pdf>


---

### Answer by username_10 on 2015-12-09. Score: 3

We can not prove terrorists are not rational. We can only have a failure to find a tractable utility function that adequately models their behavior.

On the practical side, one cannot see enough decisions from a person *ceteris paribus* to confirm much about their rationality. Too much happens over time, without observation, and in a noncontinuous manner. Perhaps we can acquire evidence that their actions have a degree of stochastic noise about them. Or that they do they do not fit model X, or we are omitting a variable Y.

On the theoretical side, for any set of behaviors, Z, one can name an array of utility functions f(Z) which would explain such behavior. I say nothing optimistic about the *simplicity*, *verification*, or *stability* of these utility functions, but they can be modeled nonetheless. We can only eliminate a fraction of those f(Z)'s empirically. We are left with some f(Z)'s that could defend their rationality, it remains possible they are rational.

Absence of evidence is not evidence of absence.


---

### Answer by username_11 on 2015-12-09. Score: -1

Terrorists are definitely rational. Each one of them maximizes their utility by blowing themselves up. Their preferences and utilities are defined by their beliefs, of course, not the reality of the situation. Their [rationality is bounded](https://en.wikipedia.org/wiki/Bounded_rationality), because they may not know that their beliefs are false or misguided.

The open question is how bounded is the terrorists' rationality. There are plenty of works out there, which I admit I haven't read, but [*Inside Terrorism* by Bruce Hoffman](http://www.rand.org/pubs/commercial_books/CB386.html) looks to be a very popular one.

> **Comments:**
> **username_10**: As economists, I note that our hinges upon the idea that our subjects are rational... just with perverse utility functions. Note that you cannot prove otherwise, there is always a more complex utility function to model a behavior.  
> **username_7**: "*Terrorists are definitely rational*". What does that even mean: Is the concept of rationality defined based on properties of terrorists?  

---

