Quote Originally Posted by Devils_Advocate View Post
On the other hand, there's no really good reason for non-living things not to have Constitution scores. Clearly some of them are tougher than others.
This is true, particularly since the introduction of undead "metabolisms" and "diets" in Libris Mortis; I've never seen the benefit of removing Con from undead and constructs and then going to great lengths to make a pseudo-Con for them (Unholy Toughness, replacing Con with something else for certain rolls, etc.). Con could very well represent the strength of an undead creature's animating force and the integrity of a construct's body, or even vice-versa for unintelligent undead and elementally-bound constructs.