Are dispositions equivalent to conditionals? Does 'x is fragile' mean the same as 'if x were dropped it would break'?
Hugh Mellor and I agree that disposition predicates are truly or falsely predicable of objects or systems. Whether a particular glass is fragile or not is a question of fact (once various ambiguities are set to one side). On the other hand, I follow Ramsey in thinking that conditionals like 'if x were dropped, it would break' are neither true nor false. One cannot be in suspense coherently whether it is true or false. One cannot assign coherently a (subjective) degree of probability to its being true.
Conditionals express judgements of conditional possibility and impossibility. Like expressions of judgements of serious possibility and impossibility and like expressions of judgements of subjective probability, they are supported by the inquirer's state of full belief and (in the case of probability judgement) the inquirer's confirmational commitment but are not entailed by it.
If I am right about conditionals, satisfaction conditions for disposition predicates cannot be supplied by invoking conditionals.
I shall attempt here to offer a brief elaboration of the position I favour without hoping to convince Hugh Mellor of its correctness. I have found out on more than one occasion that Mellor is immune to the approach to dispositions, abilities, chances and the like I favour, as well as to my ideas concerning conditionals. Immune or not, I have always found bouncing my ideas off the walls of his impregnable conceptual fortress rewarding. This confrontation is but a poor but sincere token of my friendship, respect and admiration for him and his work.
Does tossing the coin near the surface of the earth cause it to land heads-or-tails? We may plausibly claim that the coin invariably lands heads up or tails up on a toss given that it has the surefire disposition to do so. The universal regularity we can invoke here is that any coin having the surefire disposition