The Indianapolis times. [volume] (Indianapolis [Ind.]) 1922-1965, 1933-11-01
INFERENCE SET
IN RETROSPECT
BRANDED WEAK
Unable to Stand on Own
Feet as Proof of Any
Theory.
.Dietz on Science
BY DAVID DIETZ
Scripps-Hovard Science Editor

test tube and analyze its constit-
uents. But in so doing he destroys
the salt. This. he says, is an ex-
ample Of retrospective inference.
The property which We infer is
not that Of being x, but Of having
been x
He warns us that such retro
spective differences alone are dan
gerouS things upon which 10 try
and base any theory Of the universe.
We can not use them by them
selves as proofs Of the theory Of
determinism or any other theory.
To show how retrospective in
ference might be abused, Sir Arthur
asks us to suppose that there was no
way of learning the chemical con-
stitution of a gas without Destroy
ing IT,
BY hypothesis a chemist would
never know until after his ex
pertinent what substance he had
been handling so that the result
Of every experiment would be en-
tirely unforeseen he continues.
Must he then admit that the laws
Of chemistry are chaotic? "a man
of resource would override such
trifling obstacle If he were dis
Greet enough never to say before
hand what his experiment was go
ing to demonstrate. he might give
edifying lectures on the uniformity
of nature"
Our hypothetical chemist would
plunge lighted tapers into his
cylinders Of gas If they burned
more brightly, he would infer that
the cylinder had contained oxygen.
If they went out, he would say nj
trogen. If the gas itself caught fire,
he would say hydrogen.
If by retrospective inference We
infer characters at an earlier date
and then say that those characters
invariably produce at future date
the manifestation from which we
inferred them, we are working in a
circle Sir Arthur continues. The
connection is not cauSation but def
milton, and we are not prophets but
taUtOlogists.
1T is easily seen that to avoid
vicious circles we must abolish pure
" retrospective characteristics -
those which are never found as ex-
listing but always as having existed"
He admits at once that chemistry
is founded on better grounds than
the imaginary ones just sighted In
analyzing a salt, we can take a
small portion and place it in the
test tube. If We show that this
small portion has been X" it is
entirely fair to assume that the rest
lis X"
InappliCabIe to Storms
1t is sometimes argued" he saws.
that in this way a character in
ferable retrOSpeCtively must also be
1nferable cOntempOraneOusly: if
that were true it would remove all
danger of using retrospective in
ference to invent fictitious charac-
tiers as causes of the events observed.
Actually, the danger arises Just
at the point where the method of
Sampling breaks down, namely
when We are concerned with char
acteriSt!cs supposed to distinguish
one individual atom from another
atom of the same substance: for
the individual atom can not be di-
vided into two samples, one to
analyze and one to preserve"
As an example of what he means.
Sir Arthur asks us to consider the
radioactive atoms. Eventually. a
given radioactive atom exhibits its
nature by exploding. But there is
no way by which the physicist can
determine the time in the future at
which any given radioactive atom
will explode.
The time of break up of a radio
active atom is an example of ex-
IRENE indeterminiSm. he SAYS. But
It must be understood that accord
ing to current theory all future
events are indeterminate in greater
or lesser degree and differ only in
the margin of uncertainty.
Improbability Cited
When the uncertainty is below
our limits of measurement the
event is looked upon as practically
determinate; determinacy in this
sense Is relative to the refinement
of our measurements.
The statement that all phenom-
ena have some degree of indeter-
minacy probably will be criticised
as too sweeping. I viii consider Just
one example
He asks us TO consider a certain
type of potassium atom which is
considered not radioactive. Since
another type is considered radio
active We might say that we could
predict without any indeterminacy
that the nonradioactive type would
not explode.
His answer is that strictly speak
ing We can not say that we have in
hand one of the nOnradioactive DO
tassium atoms but only an atom
which has a high probability of be-
. ing one.
Such an atom should contain 80
pr0tonS WITHIN small nucleus he
says. But the proton in modern
physics has a very important pc
culiarity. namely. it never is any
where quite definitely, though it may
have a greater probability of being
in one place rather than another.
Thus We can never get beyond a
high probability of SO protons be-
ing collected together.
1t is impossible TO trap modern
physics into predicting anything
with complete determinacy. because
il deals with probabilities from the
outset
$. II. s. Graduates Chosen
-Four ShOrtridge high shOol gradu-
ates have been selected for the cast
of "FrillS and FJrbelowS." musical
comedy TO be DreSentp6 at Indiana