Re: What is a theory? LO3689

Richard Karash (
Sun, 12 Nov 1995 21:10:57 -0500 (EST)

Replying to LO3659 --

On Tue, 7 Nov 1995, John O'Neill wrote:

> It is often postulated that we reason about the world using theories of
> how we expect the world to behave. In cognitive science these theories are
> called mental models. In computer science (and mathematics?) these
> theories are called models or simulations.
> One question I have is what is a theory?

To me, a theory is when someone asserts their belief about how something
works. To me a theory is more than a description, it should be a
structural explanation. In this sense, a theory is to me just about the
same as a "model."

> The second question I have is how do we construct new theories?
> Learning (to me) is all about the construction of new theories to deal
> with situations in the real world. These new theories are often
> constructed as a result of invalidating assumptions in existing theories.
> For example, Einstein's theory of relativity arose by firstly invalidating
> the assumption that the speed of light was constant as assumed by
> Newtonian physics.

I ask this question often in my management programs. Almost everyone seems
to think that theories come from inspection of data. The popular idea is
that we see something in the data that cannot be explained by the current
theories (this seems OK to me so far...). But then, most people I ask go
on to say that the data points the way to the improved theory.

In my view, the new theory is a personal creative act.

There is a wonderful story in Michael Polanyi's _Personal Knowledge_,
Chapter I, section 3. I'll quote just a bit of it:

"The story of relativity is a complicated one, owning to the currency of a
number of historical fictions. The chief of these can be found in every
textbook of physics. It tells you that relativity was conceived by
Einstein in 1905 in order to account for the negative result of the
Michelson-Morley experiment, carried out in Cleveland eighteen years
earlier, in 1887. Michelson and Morley are alleged to have found that the
speed of light measured by a terrestrial observer was the same in whatever
direction the signal was sent out. That was surprising, for one would have
expected that the observer would catch up to some extent with signals sent
out in the direction in which the earth was moving, so that the speed
would appear slower in this direction, while the observer would move away
from the signal sent out in the opposite direction, so that the speed
would then appear faster. The situation is easily understood if we
imagine the extreme case that we are moving in the direction of the signal
exactly at the speed of light. Light would appear to remain in a fixed
position, its speed being zero, while of course at the same time a signal
sent out in the opposite direction would move away from us at twice the
speed of light.

"The experiment is supposed to have shown no trace of such an effect due
to terrestrial motion, and so -- the textbook story goes on -- Einstein
undertook to account for this by a new conception of space and time,
according to which we could expect invariably to observe the same value
for the speed of light, whether we are at rest or in motion. So Newtonian
space, which is 'necessarily at rest without reference to any external
object,' and the corresponding distinction between bodies in absolute
motion and bodies at absolute rest, were abandoned and a framework set up
in which only the relative motion of bodies could be expressed.

"But the historical facts are different. Einstein had speculated already
as a schoolboy, at the age of sixteen, on the curious consequences that
would occur if an observer pursued and kept pace with a light signal sent
out by him. His autobiography reveals that he discovered relativity 'after
ten years' reflection... from a paradox upon which I had already hit at
the age of sixteen'"

Polanyi describes checking this with Einstein himself in 1954 and then
goes on...

"The usual textbook account... is an invention. It is the product of a
philosophical prejudice. When Einstein discovered rationality in nature,
unaided by any observation... our positivistic textbooks promptly covered
up the scandal by an appropriately embellished account of his

"But there yet remains an almost ludicrous part of the story to be told.
The Michelson-Morley experiment of 1887... actually did not give the
result required by relativity! It admittedly substantiated its authors'
claim that the relative motion of the earth and the 'ether' did not exceed
a quarter of the earth's orbital velocity. But the actually observed
effect was not negligible; or has, at any rate, not been proved negligible
up to this day...

"The layman, taught to revere scientists for their absolute respect for
the observed facts, and for the judiciously detached and purely
provisional manner in which they hold scientific theories (always ready to
abandon a theory at the sight of any contradictory evidence), might well
have thought that at [the] announcement of... overwhelming evidence of a
'positive effect' ... [scientists] would have instantly abandoned the
theory of relativity."

My own background in physics makes this pretty interesting reading,
although I know it may be pretty dry to others.

I've known from my experience that people expect the data to point the
way. And, my experience is that the data seldom point the way, data just
shows the existence of a problem. So, to me, making a theory is
fundamentally a creative act, it's an assertion of personal belief, not
just a hypothesis to which we have no particular attachment.

My reference is: Michael Polanyi, _Personal Knowledge_, Univ. of Chicago
Press, 1958. ISBN 0-226-67288-3 (paperback).

         Richard Karash ("Rick") |  <>
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