A.V. Ravishankar asked:

Our daily linguistic usage and our communication is a form common sense reasoning. If it is so how
can we formalize common sense? How is common sense reasoning used in explaining
counterfactuals used in daily linguistic discourse?

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You cannot formalize common sense. We know what makes sense to us but logical formalizations
sometimes come up with nonsense. Logical validity is not the same as validity in ordinary language.
Even connectives such as "and" and "or" are not translatable between logic and English such that
they always make sense. Mark Sainsbury (you should read his book Logical Form) has used the
following example of a logically valid argument using conditionals which is not valid in ordinary
language:

(1) If Smith dies before the election, Jones will win.
(2) If Jones wins, Smith will retire from public life after the election.
(3) So, if Smith dies before the election, he will retire from public life after the election.

We can think of grounds for the premises (1) and (2) but the conclusion (3) is absurd. There are
theories which aim to provide an account of what needs to be added to logical formulations so that
they reflect ordinary language usage, but these fail to account for the above example. H.P. Grice
argues that a conditional should have assertibility. The conditional "If Ice is denser than water, it floats
in water" is true as a logical formulation because the consequent is true, but it is not a reflection of
common sense and it is not assertable. Grice's suggestion works for the ice example, but the Smith
and Jones example can't be explained by the non-assertibility of the conclusion because it is a
problem of connectives being non-translatable.

In the example "If Oswald didn't kill Kennedy, then someone else did" we have the evidence that
Kennedy was killed, and so this is highly assertable. For an ordinary conditional we need reason to
believe in the antecedent.

Counterfactuals are further from common sense. "If Oswald hadn't killed Kennedy, someone else
would have" requires additional assumptions if it is true. Sometimes there are no assumptions which
we can make, such as in the case of Michael Dummett's example: Suppose Jones is now dead and
never faced danger in his life. We have no evidence or grounds to suppose anything about the truth
of the counterfactual "If Jones had faced danger he would have acted bravely". We have no
knowledge of the counterfactual person Jones and what he might have done. On Dummett's view we
know what would make this true, i.e. that Jones was in fact brave. However, it is possible that he was
not. The talk here is of possibilities rather than good reasons for making the statement, or assertibility
as Grice would have it. There are two possible worlds which determine the truth-value of this
counterfactual and a possible world is an imagined state of affairs, at least on some accounts. On any
account it has nothing to with common sense. Read David Lewis.

Rachel Browne