are we talking about why did something happen or are we asking why or how did someone make a choice to either do something or make a selection?.
Okay, I understand your confusion. My mind was on the philosophical/semantic concept and I lost track of the grammatical construction- sorry about that!
The origin of the confusion is, I believe, in the phrase 'are we talking about...'. Maybe a better way to say it is, 'Is the question...' as in: Is the question, 'Why did something happen?' or is it, 'Why or how did someone make a choice to either do something or make a selection?'
'A reason' has to do with a conscious, human choice after mentally considering alternatives or working through possibilities using logic (however faulty).
'Cause' has to do with forces more-or-less external to the system under consideration. Action(s) and inactions have results.
'A Factor' is any one of a number of external stimuli- either mental or physical- that influence the outcome.
I hope this helps to clear things up. :infinity: