 where the conditional is understood as a material conditional. The idea behind \(R\) is that we can meaningfully tell whether or not a given item is soluble only if it is put into water. \(R\) thus provides a rule for how to introduce the dispositional predicate ‘soluble’ in application to items that have in fact been put into water. But \(R\) is silent about whether \(x\) is soluble when it is not put into water, and this means that we cannot use \(R\) to completely eliminate the predicate ‘soluble’ from the language. Though this is what Carnap explicitly embraced, many philosophers found it deeply problematic. And so philosophers of empiricist leanings continued the search for a definition schema of dispositional expressions in an extensional language (Kaila 1939, 1942; Storer 1951).