To put it simply, logical determinism is the view that what is going to happen in the
future is going to happen, and therefore is unavoidable. For instance, tomorrow it will
either rain or not rain. One of these must come about. Therefore either it is true that it is
going to rain, or it is true that it is not going to rain. But if one of these is true then,
whichever one it may be, it must come about otherwise it would not be true. And if that
one must come about then the other one is not a possible alternative.
Logical determinism is one of those views which right away appears to have something
wrong with it, although explaining exactly what is wrong may not be so easy.
The argument's central premise is that a description of the actual future
(given now, or in the past for that matter) is true. This may of course be challenged.
One way to avoid logical determinism is to deny that contingent statements about the future are
either true or false. They simply do not have one of these two truth values until the described
event takes place. This way out, however, poses certain difficulties. In order to properly
deal with future contingents, a three-valued logic must be adopted a logic that allows
for such statements as "tomorrow it will rain" and "tomorrow it will not rain" to be neither
true nor false while simultaneously maintaining the statement "tomorrow it will either rain or
not rain" to be true. This may not be too much of a problem, but if there's a simpler way out of
the dilemma, this change to logic probably should be avoided.
Let's therefore accept the premise that a description of the actual future is
true. Does the logical determinist's conclusion follow? I believe it does not. Their conclusion
is simply a non sequitur. To see this, suppose that the world is indeterministic and
that there are an infinite number of almanacs, each with a different account of the
future, such that all possible futures are described. One of the volumes will contain a
description of the actual future. This is undeniable even if the future is not yet
determined. (It is undeniable for the same reason that makes the statement
"tomorrow it will either rain or not rain" necessarily true. The almanacs cover all possible
futures, so one of them must have the correct information.) Suppose we agree to call the
information in that book "true" (though of course we do not know which book is
the one). It does not follow that the future is determined. For, as already pointed out, that
there is such a book is compatible with the future being open to other alternatives. (The same
point could of course be made with just two possible alternatives, e.g., "rain" or "no rain".
But it seems to be easier to understand the argument with a large and possibly infinite number
of possible futures, maybe because that way the indeterminism assumed in the argument is
The choice open to us is as to whether we should call a description of a future that is
as yet undetermined "true". We can choose to call it "true" and keep a two-valued logic (as
there seems to be no reason not to do this), or we can maintain that it is neither true nor false
and take up a three-valued logic. I don't think there is a substantial distinction here. It's
merely a matter of preference which way of speaking we'd rather adopt. What is not a
valid option, however, is logical determinism. For from the fact that we call a description of
the actual future "true", it does not follow that the described future must inevitably
Logical determinism is also commonly called "fatalism". That, however, is potentially
confusing, since "fatalism" is also the name for a different view, one concerning the
consequences of determinism. Fatalism in this latter sense is the thesis that all actions are
pointless because what will be will be. The classic expression of this view is
the famous "idle argument" from antiquity. According to that argument, one should not call a doctor when one is sick, for one
is already fated to either get better or else to die. If one is fated to get better, then a
doctor is unnecessary. If one is fated to die, then a doctor will be helpless to prevent it.
The error underlying fatalism of this kind lies in not realizing that our actions are
themselves part of the deterministic process. If one does not call a doctor, then that is itself
an action that was determined to happen. Furthermore, that action may be connected with it being
the case that one is fated to die. If on the other hand one does call a doctor, then one's fate
may be to survive the illness.
©2000 Franz Kiekeben