ointing to the fact "to-day
is Tuesday" if that is a fact, or away from the fact "to-day is not
Tuesday" if that is a fact. The "meaning" of the proposition "to-day is
not Tuesday" will be exactly the opposite. By this hypothetical form
we are able to speak of the meaning of a proposition without knowing
whether it is true or false. According to this definition, we know the
meaning of a proposition when we know what would make it true and what
would make it false, even if we do not know whether it is in fact true
or false.

The meaning of a proposition is derivative from the meanings of its
constituent words. Propositions occur in pairs, distinguished (in
simple cases) by the absence or presence of the word "not." Two such
propositions have the same objective, but opposite meanings: when one is
true, the other is false, and when one is false, the other is true.

The purely formal definition of truth and falsehood offers little
difficulty. What is required is a formal expression of the fact that a
proposition is true when it points towards its objective, and false when
it points away from it, In very simple cases we can give a very simple
account of this: we can say that true propositions actually resemble
their objectives in a way in which false propositions do not. But for
this purpose it is necessary to revert to image-propositions instead of
word-propositions. Let us take again the illustration of a memory-image
of a familiar room, and let us suppose that in the image the window is
to the left of the door. If in fact the window is to the left of the
door, there is a correspondence between the image and the objective;
there is the same relation between the window and the door as between
the images of them. The image-memory consists of the image of the window
to the left of the image of the door. When this is true, the very same
relation relates the terms of the objective (namely the window and
the door) as relates the images which mean them. In this case the
correspondence which constitutes truth is very simple.

In the case we have just been considering the objective consists of
two parts with a certain relation (that of left-to-right), and the
proposition consists of images of these parts with the very same
relation. The same proposition, if it were false, would have a less
simple formal relation to its objective. If the image-proposition
consists of an image of the window to the left of an image of the door,
whi