The foundation of reason

Eliezer S. Yudkowsky (
Fri, 05 Mar 1999 03:47:02 -0600

Max More wrote:
> Point: Reason is without foundation. (See Bartley's book or my version in
> the Pancritical Rationalism essay.) Does that destroy rationalism?

Reason WAS without foundation. Excerpt from a forthcoming work:


2.3:  How does the logic ground in conscious experience?

This question comes to you courtesy of the really sharp doubters, people
who assume nothing; people who doubt that the physical Universe has any
existence outside their own minds, people who in fact doubt the
existence of their own minds, people who wonder if maybe the whole
Universe came into existence a second ago complete with false

Let's start with the qualia.  "Qualia" is a technical term philosophers use
to describe the redness of red, the mysterious, indescribable, apparently
irreducible quality of redness that exists above and beyond <FONT
color="#FF0000">.  (There is a certain amount of dispute over what
qualia are or even whether the term refers to anything.)  I'm using the
term "qualia" to refer to your immediate conscious sensations, your
now - the movie screen, as it were, of your Cartesian observer, before
all rational interpretation.  (I am also referring to the qualia of any
rational interpretation you may be doing, but I'm not yet admitting them
as rational interpretations.  Got it?) 

It's an interesting question as to whether or not you can doubt that you
are right now experiencing the sensation of redness.  Some people
would say no.  I would say yes. 

Even supposing you do doubt the qualia, however, I hope you will agree
that there is not a different set of qualia which are more plausible.  So,
while you don't have to assign a 100% probability to the existence of the
qualia, there isn't anything else whose existence you are more sure of. 
Thus, choices made using this set of qualia will take precedence over

Next, we consider the question of time.  You have what may be the
illusion of existing in time.  You have the qualia of memories of the
past.  You have the qualia of memories of continuity - that you thought,
"I'll have to make this choice", and then you did make the choice.  You
have the qualia of memories of predicting the immediate and far future,
and the qualia of memories of the immediate predictions succeeding, and
of the far predictions failing in understandable ways. 

Assuming that these qualia actually represent a past and present is a
big step, however, because it involves interpretation.  It involves an
assumption that the qualia correspond to an external reality.  Moreover,
it isn't a certain assumption.  Maybe you really did come into existence a
second ago, complete with false memories.  Maybe all consciousness is
made up of unconnected instants of arbitrary qualia.  There are theories
like that, especially in really good books - i.e., books by Greg Egan - and
you may consider them as probable as you wish. 

When it comes to making choices, however, you have to assume that your
choices are meaningful, that they have effect.  I mean, maybe they do and
maybe they don't, but in order for there to be a distinction between
choices, you have to act as if they do.  And that requires consequences,
causality, before-and-after, time.  So whether or not you think your
memories are faked, you should at least accept that you exist as a
sequence of qualia, that you have a time dimension. 

Next, we ask whetherthought is valid.  Is it worthwhile to place
interpretations on qualia, relate various sets of qualia to each other,
build up a mental model of the world?  Is it worthwhile to relate choices
to qualia?  To assume that choices will affect future qualia or the
world?  To try and select between choices on that basis?  Perhaps the
mind is a phantom - haven't we "observed" people who live in phantom
worlds?  Perhaps all thought is fundamentally flawed - doesn't our
"thought" give us great catalogs of logical flaws?  Perhaps so.  But,
insofar as the only way I know of to relate to the world is to think, I
don't know of any better alternative. 

Again, it comes down to making choices.  I don't know of any way of
making choices that doesn't rely on some form of activity in the grey
matter.  Even "instinct" counts as thought, for these purposes.  We are
not now asking whether extremely sophisticated philosophy has any
validity, but whether we should admit that the mind exists and that the
basic units of cognition relate to reality, whether truly or falsely. 
And I
answer:  Denying validity to the mind doesn't result in any particular
advice, any particular preferred choices.  We may as well act as if the
mind exists, until we have evidence otherwise; or some other way of
relating to reality; or until the alternative seems more plausible and
gives specific advice. 

Next, we consider rational thought, science and logic.  Throughout this
whole page, I've been arguing using (what is arguably) science and
But does it make sense to assume that a world exists external from our
minds?  To create theories which provide opinion-insensitive
predictions for relating parts of observed reality, or relating past
observations to future relations?  To test theories by making predictions
and comparing them to experimental observations?  Sadly, many people
don't.  But the people who do are the ones who can make fifty stalks of
wheat grow where three grew before, build great towers of glass and
steel, vaporize cities, set foot on the Moon. 

There are all kinds of explanations for reality.  I believe in science.  I
believe in science simply because science has resulted in
technology; science displays the power to alter the world
rather than epiphenomenally explaining it, and that's what
makes it relevant to me as a means of relating choices to
future qualia.  The useful explanation is the one that tells you how to
change something.  And according to my qualia of memories, that means
science and intelligent thought. 

Any other justification is hokum.  If waving hands and uttering strange
whispers got results, and elaborate experimental setups never produced
anything useful, I would believe in magic instead of science.  If Ouija
boards produced better predictions than calculus, I would junk
mathematics.  Any other way would be superstition.

--         Eliezer S. Yudkowsky

Disclaimer:  Unless otherwise specified, I'm not telling you
everything I think I know.