Here's a bit of it:
The infliction of physical pain on a person with no means of defending himself is designed to render that person completely subservient to his torturers. It is designed to extirpate his autonomy as a human being, to render his control as an individual beyond his own reach. That is why the term "break" is instructive. Something broken can be put back together, but it will never regain the status of being unbroken--of having integrity. When you break a human being, you turn him into something subhuman. You enslave him. This is why the Romans reserved torture for slaves, not citizens, and why slavery and torture were inextricably linked in the antebellum South.
What you see in the relationship between torturer and tortured is the absolute darkness of totalitarianism. You see one individual granted the most complete power he can ever hold over another. Not just confinement of his mobility--the abolition of his very agency. Torture uses a person's body to remove from his own control his conscience, his thoughts, his faith, his selfhood.
....[T]he very concept of Western liberty sprung in part from an understanding that, if the state has the power to reach that deep into a person's soul and can do that much damage to a human being's person, then the state has extinguished all oxygen necessary for freedom to survive. That is why, in George Orwell's totalitarian nightmare, the final ordeal is, of course, torture. Any polity that endorses torture has incorporated into its own DNA a totalitarian mutation. If the point of the U.S. Constitution is the preservation of liberty, the formal incorporation into U.S. law of the state's right to torture--by legally codifying physical coercion, abuse, and even, in Krauthammer's case, full-fledged torture of detainees by the CIA--would effectively end the American experiment of a political society based on inalienable human freedom protected not by the good graces of the executive, but by the rule of law.
You'll find the entire essay on the New Republic site. Registration is required, but it's free. And the essay is worth it.