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Saturday, January 05, 2019


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Two purely technical points here.

1. According to Strawsonian presupposition, ‘One sentence presupposes another iff whenever the first is true or false, the second is true. On the ‘presupposition via negation’ definition, ‘One sentence presupposes another iff whenever the first sentence is true, the second is true, and whenever the negation of the first sentence is true, the second sentence is true. I prefer the first definition, but both are problematic for existential propositions.

2. In the medieval tradition, there was a lot of discussion of propositions like ‘Socrates begins to run’. According to many of the scholastics, such a proposition has two ‘exponents’. For example, ‘Socrates is now running, but immediately before this was not running’.

This is in haste, wife is shouting for me to go to lunch.

ad 1) The two definitions appears to be logically equivalent if we assume Bivalence (exactly two truth values, T and F)

If Socrates stopped talking, then he was talking. If Socrates did not stop talking, then he was talking. The consequent survives the negation of the antecedent. So by the above criteria, *Socrates was talking* is a presupposition of both conditional sentences.

Note that neither assertion, nor any other speech act, comes into the above definitions.

This is semantic presupposition which is not the same as pragmatic presupposition. The first connects propositions; the second a person and a proposition.

Now which of these is your main concern?

To avoid all confusion, let’s focus on propositions, although I suspect there will still be confusion.

p = *Socrates stopped talking*
q = *Socrates was talking*

On the view you express above, (p v not-p) entails q. Presumably you hold excluded middle, i.e. necessarily (p v not-p). Then necessarily q.

So it is necessary that Socrates was talking. Why? What if he was a deaf mute, and never talked?

>> At most, LEM is a presupposition of my assertion, and of every assertion.

True, but you need to avoid consequences of contingent propositions turning into necessary ones. If (p v not-p) entails q, then q is necessarily true. But the proposition expressed by ‘Socrates was talking’ is not a necessary truth.

>> it seems to me that what I assert on any occasion is precisely what I intend to assert on that occasion and nothing else.

We have discussed this before, and we disagree. I utter ‘Jake is thin’, but I intend to assert that Jake is thick. The word came out all wrong. According to you, what I have asserted is that Jake is thick. According to me, what I have asserted depends on the conventional meaning of the word ‘thin’, which means thin not thick.

Generally I disagree with the possibility of telepathy. We aim to show what we intend by means of sounds or symbols which have a community-wide meaning. We are not mind readers.

Is an ontology presupposed by any proposition?
Tillich: "Every epistemological assertion is implicitly ontological".
"Tony Won the Race" v an ontology.
How is an 'implication' related to an 'assertion' or to a 'presupposition' when it is an ontology that in inferred?

To be more clear:
Do all propositions imply an ontology?
Is "imply" strong enough to bear the weight of 'assertion"? Or is 'imply' basically an equivalent to 'presuppose'?

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