(intro music)
I'm Ram Neta, professor of philosophy
at the University of North Carolina, Chapel Hill,
and I'm going to talk about rationality.
Why be rational?
If you're like most people,
you think of yourself
as a generally rational person.
Although you sometimes make mistakes
in your thinking or your planning,
you tend to regard those mistakes
as resulting from errors or gaps
in the information that you receive
from memory or testimony,
rather than as resulting from your reasoning poorly
from the information that you have.
Also, if you're like most people,
you think that other people are frequently guilty
of poor reasoning
and that your own reasoning skills
are superior to theirs.
But in fact,
how good are you at reasoning?
Try answering a couple of simple questions.
First, supposed that Pat is looking at Chris
and Chris is looking at Sam.
Pat is married
and Sam is unmarried.
In this situation,
is a married person looking
at an unmarried person?
'Yes,' 'No,'
or 'Not enough information to determine'?
Most people answer
'C) Not enough information to determine,'
because although they know
that Pat is married
and Sam is unmarried,
they don't know whether Chris is married
or unmarried.
But a moment's reasoning will show
that 'C' is the wrong answer.
Even though we don't know
whether Chris is married or unmarried,
we know that Chris is either married
or unmarried.
Well, suppose Chris is married.
Then, since Chris is looking at Sam,
a married person is looking at an unmarried person.
Now suppose that Chris is unmarried.
Then, since Pat is looking at Chris,
a married person is looking at an unmarried person.
So, no matter whether Chris is married or unmarried,
a married person is looking at an unmarried person.
Let's try another question.
Consider the number ten
and the number 9.999...
Are these two different numbers
or two different names
for the same number?
Most people say
they're two different numbers.
But again, a moment's reasoning will show
that they're just two different names
for the same number.
Let x equal 9.999...
Then 10x will equal 99.999...
And since x equals 9.999...,
it follows that 9x is equal to 90.
Dividing both sides of this equation by nine,
it follows that x equals 10.
But since x equals 9.999...,
it follows that 10 equals 9.999...
The two questions I've just chosen
illustrate a general pattern:
most people,
even highly intelligent and well-educated people,
do not exert
even the small effort required
in order to reason well.
This is true
not merely when it comes to purely theoretical questions,
like the ones I've asked above.
It's also true when it comes
to practically consequential questions,
like how to invest our resources
or which consumption decisions to make.
For example, investors frequently acquire
irrationally inflated expectations
about the future growth of some asset,
thereby creating a speculative bubble
in the value of that asset.
Once investors begin to realize
that the asset's growth can't satisfy
these irrational expectations,
they respond with an equally irrational fear,
and consequently,
the asset suffers a very rapid sell-off
and rapid decline in value.
The disastrous personal and social consequences
of these booms and busts
are by now well-known.
So, other people's unfavorable views
of our own rationality
tend to be more accurate
than our own favorable view of it.
Human beings are,
to a larger extent than we care to admit,
irrational animals
and our species has paid dearly
for such irrationality.
But there are two ways of addressing the problems
created by human irrationality
We could address them
by trying to improve
human rationality,
or by trying to design systems
that accommodate
for the predictable effects
of human irrationality.
In his popular book Predictably Irrational,
Professor Daniel Ariely proposes ways
of doing the latter.
This focus on designing systems
to accommodate human irrationality
is understandable,
since, thanks to the research
of Ariely and others,
we now know much more
about how to predict human irrationality,
and so how to design regulations
and institutions that can operate
to avoid its otherwise adverse effects.
In contrast, we still know very little
about how to improve human rationality.
But if we can design regulations and institutions
that can operate to save us
from the adverse consequences
of our irrationality,
then is there any reason
to improve our rationality?
Is rationality something still to be valued,
even once we know
how to avoid the harms
that would normally result from its absence?
Presocial humans would have died very quickly
if they did not have formidable
physical strength and speed.
But we no longer think
that a person's lack of such strength and speed
is a personal failing,
since we now have tools and vehicles
that allow the weakest and slowest among us
to do more and live longer and more comfortably
than presocial humans could ever have imagined.
If we develop the social technologies
to correct for the adverse consequences
of human irrationality,
then should we continue to think
of irrationality is a personal failing?
Should we continue to value
and to try to cultivate
rationality in ourselves
and in others?
If so, then why?
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