Who is Derek Parfit?

Philosophers such as Derek Parfit, and Hume and Blain before him, who maintain that we are not continuing persons but successive series of states, do not apply their theories to real life and especially themselves. As Bradley asked of Blain, 'Mr Blain collects that the mind is a collection. Has he ever collected who collects Mr Blain?' (But then Bradley went on to argue something rather similar in Appearance and Reality .)
Parfit explicitly states we are not the same persons at all as we were in the past. So, if you were to borrow £50 pounds for a month from him today and he asked for its repayment a month later, you could ask, 'Why?' For, according to his own doctrine, you would not then be the person who borrowed it nor he the person who lent it.
Philosophy was once the search for wisdom. But now it is often the production of absurdities that the producers themselves clearly do not believe. Why, taxpayers might well ask, do we pay good salaries to such people?