tener and deber

Question

Is there a rule for when to use tener and when to use deber when you're saying "I have to (x,y,z)"? I thought it was always deber but in harry potter y la piedra filosofal:

"Tendrian que haber sentido pena por Hagrid..."

Answer 1

I was taught the "tener que" meant "you HAVE to" (little chioice involved) while deber meant "should or ought to" (less obligatory). Then there is Hay que (Haber que)....

This question has arisen in other discussions. Why don't you try searching the discussions? You can google a site that explains the different obligions implied in each term because I posted a copy of one here in another discusssion.
[url=http://my.spanishdict.com/forum/topic/show'id=1710195%3ATopic%3A314577]http://my.spanishdict.com/forum/topic/show'id=1710195%3ATopic%3A314577[/url]

[url=http://my.spanishdict.com/forum/topic/show'id=1710195%3ATopic%3A47617]http://my.spanishdict.com/forum/topic/show'id=1710195%3ATopic%3A47617[/url]

http://www.spanish-kit.net/grammar/121.html