Indicative conditionals

Under what circumstances is an indicative conditional sentence, such as 'If it rains, I will take an umbrella' true?

I defend the simplest account of such sentences, that they are true unless the antecedent is true and the consequent false, against common objections - for example, that conditionals such as 'If Glasgow is in France, then Glasgow is in South America' come out true.

The essential idea (originating with Grice) is to distinguish the circumstances in which such a conditional is true from the circumstances in which it is assertable. But this leaves open the questions
(i) what exactly are the correct assertability conditions,
(ii) what should one say about such conditionals when they occur in unasserted contexts (for example, as beliefs, or as parts of complex sentences), and
(iii) what reasons are there for believing that these are the right truth-conditions in the first place?

My project is to answer these questions.