Editing Tractatus Logico-Philosophicus (section)

===Propositions 4.''N'' to 5.''N''===

The 4s are significant as they contain some of Wittgenstein's most explicit statements concerning the nature of philosophy and the distinction between what can be said and what can only be shown. It is here, for instance, that he first distinguishes between material and grammatical propositions, noting:

{{quote|{{ubl|item_style=margin-left: 1.5em; text-indent:-1.5em|4.003 Most of the propositions and questions to be found in philosophical works are not false but nonsensical. Consequently we cannot give any answer to questions of this kind, but can only point out that they are nonsensical. Most of the propositions and questions of philosophers arise from our failure to understand the logic of our language. (They belong to the same class as the question whether the good is more or less identical than the beautiful.) And it is not surprising that the deepest problems are in fact ''not'' problems at all.}}}}

A philosophical treatise attempts to ''say'' something where nothing can properly be said. It is predicated upon the idea that philosophy should be pursued in a way analogous to the [[natural sciences]]; that philosophers are looking to construct true theories. This sense of philosophy does not coincide with Wittgenstein's conception of philosophy.

{{quote|{{ubl|item_style=margin-left: 1.5em; text-indent:-1.5em
|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.
|...
|4.113 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.}}}}

Wittgenstein is to be credited with the popularization of [[truth tables]] (4.31) and [[truth conditions]] (4.431) which now constitute the standard [[semantic]] analysis of first-order sentential logic.<ref>Grayling, A. C. ''Wittgenstein: A Very Short Introduction,'' Oxford</ref><ref>[[William Kneale|Kneale, M. & Kneale, W.]] (1962), ''The Development of Logic''</ref> The philosophical significance of such a method for Wittgenstein was that it alleviated a confusion, namely the idea that logical inferences are justified by rules. If an argument form is valid, the conjunction of the premises will be [[Logical equivalence|logically equivalent]] to the conclusion and this can be clearly seen in a truth table; it is ''displayed''. The concept of [[tautology (logic)|tautology]] is thus central to Wittgenstein's Tractarian account of [[logical consequence]], which is strictly [[deductive]].

{{quote|{{ubl|item_style=margin-left: 1.5em; text-indent:-1.5em
|5.13 When the truth of one proposition follows from the truth of others, we can see this from the structure of the propositions.
|5.131 If the truth of one proposition follows from the truth of others, this finds expression in relations in which the forms of the propositions stand to one another: nor is it necessary for us to set up these relations between them, by combining them with one another in a single proposition; on the contrary, the relations are internal, and their existence is an immediate result of the existence of the propositions.
|...
|5.132 If p follows from q, I can make an inference from q to p, deduce p from q. The nature of the inference can be gathered only from the two propositions. They themselves are the only possible justification of the inference. "Laws of inference", which are supposed to justify inferences, as in the works of Frege and Russell, have no sense, and would be superfluous.}}}}