From a Thomistic point of view, those who say that happiness is not the ultimate purpose, or that happiness is not an end in itself, are usually making at least one of two mistakes. Either they are confusing happiness with pleasure, and saying that pleasure is not an end in itself, which is true; why pleasure cannot be our ultimate purpose is explained in Question 2, Article 6. Or else they are failing to distinguish the ultimate purpose in the sense of the thing itself that is to be attained (which is God) with the ultimate purpose in the sense of the attainment or enjoyment of that thing; this distinction is discussed in Question 1, Article 8, Question 2, Article 7, and Question 3, Article 1.