Can we treat humans without a rational capacity as property?

[tnunamak]

Then this hypothetical person is a broken unit, correct? If he/she were not, then the definition of man would have to be modified from "rational animal" to "usually rational animal."

What I don't like about this idea is that you're essentially saying that an individual's rights do not depend on his individual nature. If I were physiologically an ape who, by some mutation, gained a complete rational faculty, I would hope that I'd have the appropriate rights which most apes would not.

Even is one held that only beings with a rational faculty have rights, you would have to have strong and objective criteria for distinguishing "clearly has no rational faculty" (dogs and trees) from "might have a rational faculty" (people with damaged brains).

Don't we already do this for children and criminals?

[DavidOdden]

Then this hypothetical person is a broken unit, correct?

Right.

What I don't like about this idea is that you're essentially saying that an individual's rights do not depend on his individual nature.

I understand, but remember that rights are about interactions between people, and they are conceptual statements of that which you may or may not do as a member of a civilized society. That means a society governed by objective law, both objectively stated and justified according to objective principles. An objective law against murder could prohibit the killing of a rational being, or the killing of a man (or human, to avoid the meaning "adult male"). There isn't any serious question of identification when it comes to asking what is a human, and that is the reason why the descriptions of rights (and the prohibitions against rights-violations) are carried out in terms of the concept "human", not "rational animal". There are very serious questions that arise when it comes to identifying the referent of "rational being". That is a serious problem, given the requirement for objective law, since objective law is a law where any man can know what he is not allowed to do, and what the penalty will be for violating the prohibition. If laws were stated with reference to "having a rational faculty", you would be in a terrible bind in that you would not be able to know in advance whether some being had a rational faculty and had rights, or was meat. The existing concept of rights, stated in terms of the obvious fact "human", is perfect for statements about rights.

If I were physiologically an ape who, by some mutation, gained a complete rational faculty, I would hope that I'd have the appropriate rights which most apes would not.

And if my grandmother had balls... Seriously, not only are you not a mutated gorilla, but there is no such thing as a mutated gorilla with a rational faculty. I could imagine such a thing coming about, and if it did, some new concept would have to be formed; and I agree that you and DW should have rights. A new concept would have to be formed, and the consequence would / should be that the concept "rights" would apply to humanoids or whatever they're to be called.

Don't we already do this for children and criminals?

No, because there is no question that they have a rational faculty. You didn't mean criminals, did you? With children, the problem is not the lack of a rational faculty, but rather the inability to use it sufficiently. Remember that a rational faculty is just a faculty, an ability. You still have to have something for this abstract capacity to work on, thus you have to understand "causality", "obligation" and so on.