The theory advanced to explain why some phenomen occurs
cannot be tested.
We test a theory by means of its predictions. For
example, a theory may predict that light bends under
certain conditions, or that a liquid will change colour
if sprayed with acid, or that a psychotic person will
respond badly to particular stimuli. If the predicted
event fails to occur, then this is evidence against
A thoery cannot be tested when it makes no predictions.
It is also untestable when it predicts events which would occur
whether or not the theory were true.
- Aircraft in the mid-Atlantic disappear because of the
effect of the Bermuda Triangle, a force so subtle it
cannot be measured on any instrument.
(The force of the Bermuda Triangle has no effect other
than the occasional downing of aircraft. The only possible
prediction is that more aircraft will be lost. But this
is likely to happen whether or not the theory is true.)
- I won the lottery because my psychic aura made me win.
(The way to test this theory to try it again. But the person
responds that her aura worked for that one case only. There
is thus no way to determine whether the win was the result
of an aura of of luck.)
- The reason why everything exists is that God created
(This may be true, but as an explanation it carries no
weight at all, because there is no way to test the theory.
No evidence in the world could possibly show that this theory is
false, because any evidence would have to be created by God,
according to the theory.)
- NyQuil makes you go to sleep because it has a dormative
(When pressed, the manufacturers define a "dormative formula"
as "something which makes you sleep". To test this theory, we
would find something else which contains the domative formular
and see if makes you go to sleep. But how do we find something
else which contains the dormative formula? We look for things
which make you go to sleep. But we could predict that things
which make you sleep will make you sleep, no matter what the
theory says. The theory is empty.)
Identify the theory. Show that it makes no predictions, or
that the predictions it does make cannot ever be wrong, even
if the theory is false.
Cedarblom and Paulsen: 161
13 August 1996