David Gould said:
Doesn't this make it a privilige, not a right? In other words, it is something granted by society and which can be withdrawn at socities pleasure. This is why I find rights language so confusing and difficult to deal with.
Rights are not granted by society; they arise from the natural law. Society ought to preserve rights.
I guess it comes down to this: what is the practical difference between a right and a privilege?
The difference lies on whether they are essential or not to the accomplishment of their possessor's end. Let me explain this better:
The end of human life is happiness. And not the "happiness" of a pig or of a dog, but the happiness of a man, that is reached through the use of reason (natural happiness, imperfect) and with faith and worshipping of God (supernatural happiness, perfect).
To achieve happiness, men need many things: they need to live, they need health, food, they need to be able to choose where they go, they need to own things, to interact with others, to learn, etc. Those who are deprived of one or many of these will be severely hindered in his strive for natural happiness.
(and here I make a parenthesis: many people give up some of those so that they may better achieve perfect happiness; this is not wrong at all; though natural and perfect happiness are not in conflict with one another, man's fallen state makes him prone to value things wrongly, and thus the search for natural happiness will often hinder that for supernatural happiness; and notice that many men go even further in their error, by valuing an animal's happiness, mainly bodily pleasure, before the higher happiness that consists in living according to reason).
In the case of a class, the right is essential for accomplishing the end of that class. For example, a teacher has the right to give orders and to be obeyed inside the classroom by his students; without this, he could not teach.
Now, privileges are extra goods, not necessary to the well-accomplishment of the task. A teacher may have the privilege to eat for free in the cafeteria.
A privilege may even be unjust, as when someone has the privilege to order people to be killed. A right, on the other hand, is never unjust per se, though it may be just to take someone's rights away, for the sake of justice, or trampled in extreme cases and emergencies.