In the Tractatus, Wittgenstein draws a demarcation among meaningful sentences (1), the meaningless propositions of logic (2: sinnlos sätze) and nonsensical propositions (3: unsinnig sätze).

1) Sentences of the first type are informative since I can decide to express agreement or disageement with the truth-possibilities of their constitutive indipendent elementary sentences;

2) Tautologies of logic suffer from being informative vacuous and therefore I have no other option than expressing agreement with them all;

3) the nonsensical propositions have no truth possibilities can be referred to, for they lack any correct logical form.

Given the assumption above, in accordance with the extensional scheme of the Tractatus, Wittgenstein had to manage with the problem of the perfection of natural language in order to comply with it, since natural language is affected by vagueness ->

Both Russell and Wittgenstein recognized the phenomenon of vagueness in ordinary language; however, their explanations of it differ substantially. The standard explanation of vagueness is most often stated in terms of unclear cases of the application of a predicate (a word) or con- cepts that do not have sharp cut-off points.

I'm not sure to have grasped what a "vague sentence" precisely is and so I need some examples; may I considere, for instance, the following? -> "This chair is light brown"

It seems to me it is an example of "vague" sentence of natural language since the predicate "light brown" is not a borderline case of brown results and therefore it doesn't have a precise definition: is it correct to say that?

If it is, may I say that such sentence is still meaningful, for it has an underline logical form which is different from the surface grammar, but I can still fully interpret it semantically?

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    See Vagueness. Mar 20, 2016 at 17:06
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    On B.Russell and vagueness, see On Vagueness (1923) and Nadine Faulkner, Russell and Vagueness. Mar 20, 2016 at 17:10
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    As regards your example "this chair is light brown", it is not the predicate "light brown" that is supposed to be a borderline case but rather the object, the chair. And telling whether or not it actually is a borderline case of course depends on the chair in question. But a predicate is said to be vague if it has borderline cases, i.e. if there are objects for which it is undecided whether or not the predicate applies to them. A good example is the predicate "bald" (presumably many ordinary language predicates are vague).
    – E...
    Mar 20, 2016 at 19:07

1 Answer 1


Some comments.

In On Vagueness (1923) Russell writes:

In an accurate language, meaning would be a one-one relation; no word would have two meanings, and no two words would have the same meaning. In actual languages, as we have seen, meaning is one-many.

See Tractatus (1922):

4.111 Philosophy is not one of the natural sciences. [...]

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.

And see Ramsey's comment (1923) on it:

Let us now pass to Mr Wittgenstein's account of philosophy. "The object of philosophy," he says, "is the logical clarification of thoughts. Philosophy is not a theory but an activity. A philosophical work consists essentially of elucidations. The result of philosophy is not a number of 'philosophical propositions', but to make propositions clear. Philosophy should make clear and delimit sharply the thoughts which otherwise are, as it were, opaque and blurred" (4.112).

The above carachterization of the role of philosophy is common to the first phase (Tractatus) and the second phase (Philosophical Investigations) of W's philosophy: the elucidations of problems.

What drastically changes is the dismissal of the "project" of a perfect language, immune from vagueness, and the acceptance of the "real life" language, with its multiplicity of meanings, to be analyzed with the concepts of language game and family resemblance.

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