 The reason why and reason for thinking that conditions may help to shed light on the peculiarities encountered earlier. That I opened the door is a reason for thinking that I used the key, not a reason why. In case (iii) above, that he learns to play the instrument is the reason why I will buy Lambert a cello, and that I buy him a cello is (in the same case) a reason for thinking that—but not a reason why—he has learned to play the instrument. Our celebrating is a reason for thinking that Audrey has won the race in case (ix), but is unlikely to be a reason why.