Grice was fascinated by the misuse, by people (rather than chimps -- cfr. "Chimps can talk"), of 'because'.
The bridge collapsed because...
In his John Locke lectures, Grice distinguishes between justificatory and explanatory reasons. He then finds that he is not explaining or justifying his distinction too well and grants that there may be justificatory-cum-explanatory reasons, too!
The John Locke lectures audience was delighted!