Franz Brentano_The True and the Evident.pdf

94 Appendix 1: On the General Validity of Truth and the Basic Mistakes
(3) Naturally the situation would be entirely different if one were to prove that there is
a topoid of four or more dimensions. For then there would be an analogue of our threedimensional
geometry; and such a discipline (if we think of geometry as a science of
bodies) would belong with the natural sciences.
There is one point of view from which, even today, the so-called metamathematical
considerations might be classified along with geometry. This is the practical one of division
of work. It is the one Marty indicated, in his important address as Rector, in order to prove
the unity of philosophy. Indeed nothing more is necessary in order to show that, from this
practical point of view, knowledge of metamathematics and knowledge of geometry are
intimately connected. But it is essential to note that this point of view must be distinguished
from the theoretical one. I would refer you to Marty. 15
A certain economy is also required in logic considered as an art; this would seem to
me to preclude such logic going into metamathematical doctrines. At least if the logic is a
general logic. A logic adapted to the practical discipline just referred to should give detailed
consideration to those artifices designed to compensate for the failure of our intuition in
connection with the fourth dimension and such like. I have in mind, in particular, the
method of projection into a three-dimensional space.
II
Draft of a letter from Brentano to Husserl
On Pure Logic 16
Florence, 30 April, 1905
If I understand correctly, you would hope to take all those evident truths which are said to
be conceptually illuminating and unify them within a special theoretical discipline, and you
would call this discipline “logic”.
That there are such conceptually illuminating truths is beyond doubt. And it is undeniable
that, as such, they have something in common. But you must admit yourself that they
cannot possibly be unified.
To what extent you hope to succeed in this is still not sufficiently clear to me.
Nor is the leading thought sufficiently clear. It is not supposed to be a practical one; it is
all supposed to be done in a purely theoretical interest.
Anything that is known may well be of some theoretical interest. Knowledge, even
of the most insignificant kind, is a good. But much of it, from the theoretical standpoint,
is relatively worthless. The historian who does not exclude from his account most of the
things that he finds to have happened is dull and vapid. But so too for the one who is
concerned with general laws. How absurd it would be to prepare a book which contained
nothing from beginning to end but multiplications of numbers taken at random. Yet each
would express a general law.