popper-logic-scientific-discovery

198
some structural components of a theory of experience
69 LAW AND CHANCE
One sometimes hears it said that the movements of the planets obey
strict laws, whilst the fall of a die is fortuitous, or subject to chance. In
my view the difference lies in the fact that we have so far been able
to predict the movement of the planets successfully, but not the
individual results of throwing dice.
In order to deduce predictions one needs laws and initial conditions;
if no suitable laws are available or if the initial conditions cannot be
ascertained, the scientific way of predicting breaks down. In throwing
dice, what we lack is, clearly, sufficient knowledge of initial conditions.
With sufficiently precise measurements of initial conditions it would
be possible to make predictions in this case also; but the rules for
correct dicing (shaking the dice-box) are so chosen as to prevent us
from measuring initial conditions. The rules of play and other rules
determining the conditions under which the various events of a random
sequence are to take place I shall call the ‘frame conditions’. They
consist of such requirements as that the dice shall be ‘true’ (made from
homogeneous material), that they shall be well shaken, etc.
There are other cases in which prediction may be unsuccessful. Perhaps
it has not so far been possible to formulate suitable laws; perhaps
all attempts to find a law have failed, and all predictions have been
falsified. In such cases we may despair of ever finding a satisfactory law.
(But it is not likely that we shall give up trying unless the problem does
not interest us much—which may be the case, for example, if we are
satisfied with frequency predictions.) In no case, however, can we say
with finality that there are no laws in a particular field. (This is a
consequence of the impossibility of verification.) This means that my
view makes the concept of chance subjective.* 1 I speak of ‘chance’ when
our knowledge does not suffice for prediction; as in the case of dicing,
where we speak of ‘chance’ because we have no knowledge of the initial
conditions. (Conceivably a physicist equipped with good instruments
could predict a throw which other people could not predict.)
In opposition to this subjective view, an objective view has sometimes
been advocated. In so far as this uses the metaphysical idea that
* 1 This does not mean that I made any concession here to a subjective interpretation of
probability, or of disorder or randomness.