4.1 Propositions represent the existence and non-existence of states of
affairs.


4.11 The totality of true propositions is the whole of natural science (or
the whole corpus of the natural sciences).


4.111 Philosophy is not one of the natural sciences. (The word 'philosophy'
must mean something whose place is above or below 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.