counterfactuals

Question 1

Counterfactual statements

Answer 1

• conditional statements
  If kangaroos had no tails, they would topple over

If Alan gets a payrise, he’ll buy a Harley.
• FALSE if Alan gets a payrise but doesn’t buy a Harley
• TRUE if he gets both
• TRUE if he doesn’t get a payrise but buys a Harley anyway (eg. inherits/wins Lotto, etc.)

Question 2

truth value of the antecedent in counterfactual statements

Answer 2

> If I had taken the 5 o’clock train, I would have been killed or injured.
If I had taken the 5 o’clock train, I would NOT have been injured.
If the French explorers had decided that Western Australia was to become a settlement, we’d be having
this lecture in French.

Antecedent is F but we reason on the basis that it is T
> we treat antecedent as HYPOTHETICAL, not false

> we are asking adressee to IMAGINE -> assume antecedent is true in SOME POSSIBLE WORLD

What kind of possible world?
> as close to w0 as possible
> hierarchy of worlds in terms of ‘closeness’ to w0 depends on how many facts are different
Example:
If kangaroos had no tails they would topple over.
1. w1: Kangaroos have no tails; other facts are the same as in w0 apart from direct consequences (eg. no kangaroo tail soup)
2. w2: Kangaroos have no tails and Earth’s gravity is less than that of the real moon
3. w3: Kangaroos have no tails and have evolved a ‘walking style’
4. w4: Kangaroos have no tails. When they are weaned, they are given gas-powered jet thrusters mounted on a
harness
- Only in w1 do they ‘topple over’
»> w1 is closest to w0

Question 3

Evaluating a sentence containing a modal expression involves taking into account worlds
that are relevant (‘accessible’)

Answer 3

> necessity requires that the proposition be true in all relevant (and Best) worlds
possibility in at least one such world