Ideas of Dorothy Edgington, by Theme

[British, fl. 1997, Professor at Oxford University, and at Birkbeck, London.]

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4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / c. Derivation rules of PL
Conditional Proof is only valid if we accept the truth-functional reading of 'if'
10. Modality / A. Necessity / 1. Types of Modality
There are two families of modal notions, metaphysical and epistemic, of equal strength
10. Modality / A. Necessity / 5. Metaphysical Necessity
Metaphysical possibility is discovered empirically, and is contrained by nature
10. Modality / A. Necessity / 6. Logical Necessity
Logical necessity is epistemic necessity, which is the old notion of a priori
Broadly logical necessity (i.e. not necessarily formal logical necessity) is an epistemic notion
An argument is only valid if it is epistemically (a priori) necessary
10. Modality / B. Possibility / 6. Probability
A thing works like formal probability if all the options sum to 100%
Truth-functional possibilities include the irrelevant, which is a mistake
Conclusion improbability can't exceed summed premise improbability in valid arguments
10. Modality / B. Possibility / 8. Conditionals / a. Conditionals
It is a mistake to think that conditionals are statements about how the world is
Validity can preserve certainty in mathematics, but conditionals about contingents are another matter
10. Modality / B. Possibility / 8. Conditionals / b. Types of conditional
Maybe forward-looking indicatives are best classed with the subjunctives
Simple indicatives about past, present or future do seem to form a single semantic kind
There are many different conditional mental states, and different conditional speech acts
10. Modality / B. Possibility / 8. Conditionals / c. Truth-function conditionals
Truth-function problems don't show up in mathematics
Are conditionals truth-functional - do the truth values of A and B determine the truth value of 'If A, B'?
'If A,B' must entail (A & B); otherwise we could have A true, B false, and If A,B true, invalidating modus ponens
Inferring conditionals from disjunctions or negated conjunctions gives support to truth-functionalism
The truth-functional view makes conditionals with unlikely antecedents likely to be true
Doctor:'If patient still alive, change dressing'; Nurse:'Either dead patient, or change dressing'; kills patient!
10. Modality / B. Possibility / 8. Conditionals / d. Non-truthfunction conditionals
A conditional does not have truth conditions
X believes 'if A, B' to the extent that A & B is more likely than A & B
Non-truth-functionalist say 'If A,B' is false if A is T and B is F, but deny that is always true for TT,FT and FF
I say "If you touch that wire you'll get a shock"; you don't touch it. How can that make the conditional true?
10. Modality / B. Possibility / 8. Conditionals / e. Supposition conditionals
Conditionals express what would be the outcome, given some supposition
On the supposition view, believe if A,B to the extent that A&B is nearly as likely as A
10. Modality / B. Possibility / 8. Conditionals / f. Pragmatics of conditionals
Truth-functionalists support some conditionals which we assert, but should not actually believe
Does 'If A,B' say something different in each context, because of the possibiites there?