This is something that's always bothered me about the classic "yeshivish" presentation of Judaism.

Most "yeshivish" people will claim that the yetzer hara is an entity that is almost completely separate from a person. This bothers me, because it feels like it's just a cop-out, just an excuse so people can absolve themselves from being fully responsible their bad actions ("It's not me, really; the yetzer hara made me do it!").

So i want to know if the yetzer hara is really something that can be considered separately from the human being. If my basic Hebrew skills aren't failing me, the word "yetzer" does actually mean something like "Evil Inclination" (how "yetzer hara" is usually translated) or "nature," and doesn't necessarily refer to something external to the person, I think. Therefor, I don't think that just any reference to yetzer hara will suffice to establish "yetzer hara as a separate entity."

Is the yetzer hara a separate entity from a person? If so, what is the earliest reference to this in Judaic literature?

(Bonus: If it is true that the yetzer hara is not a part of a person, how is this not somehow escapist?)