elow the
natural sciences, not beside them.)

4.112 Philosophy aims at the logical clarification of thoughts.
Philosophy is not a body of doctrine but an activity. A philosophical
work consists essentially of elucidations. Philosophy does not result
in 'philosophical propositions', but rather in the clarification of
propositions. Without philosophy thoughts are, as it were, cloudy
and indistinct: its task is to make them clear and to give them sharp
boundaries.

4.1121 Psychology is no more closely related to philosophy than
any other natural science. Theory of knowledge is the philosophy of
psychology. Does not my study of sign-language correspond to the study
of thought-processes, which philosophers used to consider so essential
to the philosophy of logic? Only in most cases they got entangled in
unessential psychological investigations, and with my method too there
is an analogous risk.

4.1122 Darwin's theory has no more to do with philosophy than any other
hypothesis in natural science.

4.113 Philosophy sets limits to the much disputed sphere of natural
science.

4.114 It must set limits to what can be thought; and, in doing so, to
what cannot be thought. It must set limits to what cannot be thought by
working outwards through what can be thought.

4.115 It will signify what cannot be said, by presenting clearly what
can be said.

4.116 Everything that can be thought at all can be thought clearly.
Everything that can be put into words can be put clearly.

4.12 Propositions can represent the whole of reality, but they cannot
represent what they must have in common with reality in order to be able
to represent it--logical form. In order to be able to represent logical
form, we should have to be able to station ourselves with propositions
somewhere outside logic, that is to say outside the world.

4.121 Propositions cannot represent logical form: it is mirrored in
them. What finds its reflection in language, language cannot represent.
What expresses itself in language, we cannot express by means of
language. Propositions show the logical form of reality. They display
it.

4.1211 Thus one proposition 'fa' shows that the object a occurs in
its sense, two propositions 'fa' and 'ga' show that the same object is
mentioned in both of them. If two propositions contradict one another,
then their structure shows it; the same is true if one of them follows
from the other. And so on.

4.121