Mercier and Sperber's argumentative theory of reasoning proposes that: 1) Reasoning evolved primarily for argumentation, not for personal inference or belief formation. It allows humans to construct arguments to convince others and evaluate arguments from others. 2) Reasoning is thus best seen as a communication faculty rather than a truth-seeking process. It helps increase the sharing of information between individuals. 3) Predictions of this theory include that people are biased in their reasoning to find arguments that support their own views, and reasoning in groups tends to be more effective than alone.

1. Mercier and Sperber’s
evolution of argument thesis
John Wilkins
IARPA Critical
Thinking Project

2. The argument
“If we accept a conclusion because of an argument in its favor that
is intuitively strong enough, this acceptance is an epistemic
decision that we take at a personal level. If we construct a
complex argument by linking argumentative steps, each of which
we see as having sufficient intuitive strength, this is a personal-
level mental action. If we verbally produce the argument so that
others will see its intuitive force and will accept its conclusion, it is
a public action that we consciously undertake. The mental
action of working out a convincing argument, the public action of
verbally producing this argument so that others will be convinced
by it, and the mental action of evaluating and accepting the
conclusion of an argument produced by others correspond to what
is commonly and traditionally meant by reasoning (a term that can
refer to either a mental or a verbal activity). [59, emphasis added]

3. Reasoning as adaptation
“... we are not arguing against the view that our reasoning
ability may have various advantageous effects, each of
which may have contributed to its selection as an
important capacity of the human mind. We do argue,
however, that reasoning is best adapted for its role
in argumentation, which should therefore be seen
as its main function. [59, emphasis and underscore added]
• Not inference or cognition
• Intuitive inference, a sub-personal process
• Reasoning for justification to oneself and to others
• A dual process (system 1 and system 2 style) account

4. Reasoning is a
communication faculty
“Reasoning contributes to the effectiveness and reliability of
communication by allowing communicators to argue for
their claim and by allowing addressees to assess these
arguments. It thus increases both in quantity and in
epistemic quality the information humans are able to share.
[60]
“To avoid being victims of misinformation, receivers must
therefore exercise some degree of what may be called
epistemic vigilance (Sperber et al. 2010). The task of
epistemic vigilance is to evaluate communicator and the
content of their messages in order to filter communicated
information. [60]

5. The core claim
“Our claim is that argumentation is the main
function of reasoning, and we tried to demonstrate
this claim by showing the signature of this function
in the way reasoning actually functions, and in
particular in what has been seen as flaws and that
we argue are features of reasoning. [96]
• M&S do not deny that it may be used for personal
belief revision
• They do deny that reasoning is used internally in
belief construction; rather, we use intuitive inference

6. 5 Predictions of
Argumentative Theory
“ Prediction #1. If reasoning evolved so that we can argue with others,
then we should be reasonably good at arguing. Short answer: we are.
“ Prediction #2. If reasoning evolved so we can argue with others, then
reasoning should yield better results in groups than alone. Short answer: it
does.
“ Prediction #3. If reasoning evolved so we can argue with others, then we
should be biased in our search for arguments. … Accordingly, reasoning
should display a confirmation bias: it should be more likely to find
arguments that support our point of view or rebut those that we
oppose. Short (but emphatic) answer: it does, and very much so.
“ Prediction #4. When people reason alone, there is o$en nothing to hold their
confirmation bias in check. … this is very much the case.
“ Prediction #5. When reasoning is used to make decisions, it will do what
it is supposed to do, namely, find arguments. As a result, instead of always
pointing towards a better choice, reasoning wi% usua%y lead us to a decision that
is easy to justify.
From https://sites.google.com/site/hugomercier/theargumentativetheoryofreasoning

7. The problem with adaptation
stories
• Cheap and easy
• Limited by imagination (problem of null
hypothesis!) – “Justsoism”
• Fitness is not determined by a “main” function
• Hard to test (selective sweep analyses are
impossible with something already adaptive)
• Possible other explanations
• Suboptimality
• Incomplete selection
• Byproduction (spandrels)
• Evolutionary debunking arguments

8. Truth tracking and fitness
tracking
“For communication to have evolved, it had to be
advantageous to both communicators and receivers (who
are, of course, the same individuals but acting in two
different capacities). What makes communication
advantageous to receivers is that it provides them with
rich information that they could not, or not easily, have
obtained on their own. For this, the information they
receive has to be genuine information; that is, close
enough to truth. What makes communication
advantageous to communicators is that it allows
them to achieve some desirable effect in the
receivers. For this, the information they emit has to be
conducive to this effect, whether it is true or false. [96]

9. Adaptive cognition tracks
fitness enhancement
• Because of Type I–Type II tradeoffs, falsity is
sometimes adaptive
• E.g., Traditional behaviours (“We have always done
it that way”)
• Is reasoning tracking ecological or social selection
pressures?
• Why not both in different instances?
• When presenting argument publicly, then gaining
agreement is the enhancer
• When revising beliefs, ecological fitness may be
crucial

10. Criticisms of Argumentative
Theory
• Catarina Dutilh Novaes: It’s Reductionist
1.It reduces reasoning to inherently social experiences
2.It reduces reasoning to inherently linguistic
experiences
3.It fails to appreciate the strong presence of
cooperative forms of dialogical interaction

11. Criticisms of Argumentative
Theory
• Massimo Pigliucci: It’s Strange
1.there isn’t a single new datum to back up the
central hypothesis
2.“the very idea that one can meaningfully talk about
“reasoning” as if it were a well defined biological
trait, like having a prehensile tail” [is strange]
3.easy to spin evopsych scenarios

12. Criticisms of Argumentative
Theory
• John Horgan: It’s a Truism
• it’s just a truism dressed up in cognitive-
Darwinian lingo
“I suspect that some folks like argumentative
theory less because of its intrinsic merits than
because it appeals to their intellectual biases,
just as the theory might predict”
• Another example of confirmation bias?

13. Virtues and value
• Deals with a neglected aspect of reasoning (the
Philosophical, or Cartesian, Bias)
• Reason is [also] a public process as well as a
personal process of cognition
• Emphasises bias
• We seek arguments that serve our prior biases
• Emphasises communication
• Information costs, type I and II errors, signalling
theory
• ???