 One difficulty with (a), and so with (a) and (b), is that it leaves open how the relevant dispositions must be grounded. You could be disposed to believe that there was music playing next door because someone told you it was, and yet, it seems, not hear or even seem to hear any music: you might be totally deaf, for instance. In this case you would not have any auditory experience of music, despite being disposed to believe that music is playing. So proponents of (a) seem well-advised to specify an appropriate ground for the dispositions they identify with experiences, so that they do not misclassify as experiences events that intuitively are not experiences.