Full Idea
To make my emotion intelligible [in a weakness of will case] is to look back and recognise that my emotions and dispositions were not quite as I had taken them to be. It is quite useless in such a case to invoke a blanket diagnosis of 'irrationality'.
Gist of Idea
Akrasia is intelligible in hindsight, when we revisit our previous emotions
Source
Simon Blackburn (Ruling Passions [1998], p.191)
A Reaction
So Blackburn rejects the idea of akrasia, because there was never really a conflict. He says rational people always aim to maximise their utility (p.135), and if their own act surprises them, it is just a failure to understand their own rationality.
Book Reference
Blackburn,Simon: 'Ruling Passions' [OUP 2000], p.191