Distinguish Possibility from Consistency Daniel von Wachter - - PowerPoint PPT Presentation

Distinguish Possibility from Consistency

Daniel von Wachter http://von-wachter.de International Academy of Philosophy in the Principality of Liechtenstein, iap.li

Bratislava, 15 October, 2014

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Questioning assumptions

Hermann Lotze 1874 about ‘synthetic judgements a priori’: ‘We defend here a crucial element of German philosophy, for which we are attacked by all nations.’ Phenomenology: There are true modal statements about the world. Logical empiricism: understand all modality in terms of contradictions. Today instead: Understand modality in terms of possible worlds.

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Questionable assumptions

1 Question the empiricist rejection of primitive

modality.

2 Question the assumption that analytic sentences

are paradigm cases of necessity statements.

3 Question: ‘Within truth there are the modes of

truth, ways of being true: necessary truth and contingent truth.’ (Ted Sider)

4 Question the method of ontological commitments.

I do not analyse the modal concepts, they are

• primitive. I want to describe.

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Pradigms of modal statements

Not analytic statements. Not ‘p is contradictory/coherent’. ‘There cannot be a tone without a pitch’ ‘One cannot be guilty for something one did not do freely’ ‘It is possible that there exists something that is 3 kgs and has a charge of 5 C.’ ‘It is impossible that there is something that has charge but no mass.’ ‘It is impossible that there is something that is jealous and has spin 1/2.’

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How do modal questions arise?

Humans have the ability to construe descriptions

• f things by combining predicates.

The properties referred to may or may not be combinable. For every consistent combination or predicates the question arises whether the existence of a thing to which they all apply is possible. We know that some properties are combinable, but not that all are. For inconsistent descriptions, no modal questions arise.

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The difference between consistency and possibility

Two predicates are contradictory if the one is used in order to say of something, amongst other things, that the other one does not apply. If A and B are consistent predicates whose objects are incompatible, that may but need not be a priori obvious. Contradictoriness is something very different from

• impossibility. Being contradictory is something

conceptual, modality is not. Consistency is a precondition for the truth of a modal statement as for any other statement.

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The form of modal statements

1 It is possible that there is something that is A

and B.

2 It is possible that there is nothing that is A and

B.

3 It is necessary that there is something that is A

and B.

4 It is impossible that there is something that is A

and B. (Then it is true that ‘if something is A, then it is not B’)

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Conclusion

For any consistent set of predicates, the question arises whether the existence of something to which they all apply is possible. For an inconsistent set of predicates, this question does not arise. Because consistency and possibility are very different phenomena, we should say: Consistency is not a kind of possibility; contradictoriness is not a kind of impossibility. Stop using ‘logical possibility’. Modal concepts are primitive (not composed). The empiricist worries are misguided.

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Only one kind of modality

‘Logical necessity’ is analyticity and no kind of necessity, ‘logical possibility’ is consistency and no kind of possibility. Laws of nature might be necessary, but that would not be an extra kind of necessity. There are degrees of how possible something is, depending on hard or likely it is to be realised. Chalmer’s objection: if modality were not reducible to contradictoriness, that would be modal dualism. My reply: monism, ‘logical possibility’ is not possibility.

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Two kinds of entailment

P logically entails Q if ‘P and not Q’ is contradictory. P synthetically entails Q if it is impossible that P and not Q.

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Necessary predications

Is there a real question whether it is necessary that the rose is red?

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Composed concepts

Concept A is a part of concept B: ‘B’ is used in

• rder to say about something, amongst other

things, that it is A. Few concepts are composed, and they are easy to

• analyse. Analysing composed concepts is not the

main philosophical task. Instead: Describe what falls under them.

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‘Water is H2O’

Question whether there is a modal question here. Many think that this is the only synthetic

• modality. I have defended a different kind of

synthetic modality.

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