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Part I: Rationality and Other Criteria.

We are still faced with the problem of how to define persons. So far we have discussed the main positions in philosophy of mind. It identifies persons either with their bodies (materialism) or with their conscious experiences (idealism and dualism); we also discussed the social definition of persons. Now is the right time for a broader discussion of who persons are.

There are various ways to define the word "person". The term comes from Latin word persona which in its original sense means "a character or personage" acted by an actor in a theater. But the term was used early on to refer to a "human being", in particular "emphatically, as distinguished from a thing or a lower animal". In this sense Blackstone says, arguing against slavery as early as 1766: "The objects of dominion or property are things, as contradistinguished from persons". [The Oxford English Dictionary Oxford University Press 1971 p. 2140.] Hence, persons may have to be distinguished from things in terms of their special value -- this point leads us to the issue of dignity which we discuss in Division 3 of the class.

Many philosophers believe that this special value of persons relies on a specific defining property (this means a property that all persons and nobody but persons possess). The most common candidates for such a defining property of persons are either rationality or self-consciousness.

Rationality
Philosophers such as Immanuel Kant think that rationality is a distinct feature of persons. This position implies that to be a person means to be a rational being and that one cannot be a person unless one is rational.

Other philosophers think that in order to be termed a person, one must have a certain level of consciousness of one's own consciousness. This definition is similar to the understanding of persons developed by idealists and dualists. As you remember, their conception of persons also relies on consciousness since a person needs to possess consciousness. However, the present definition which refers to self-consciousness is more demanding. It maintains that a person is a creature who is not only conscious (many animals are) but who knows that she is conscious. To put it differently, by this definition it is not enough for a person to have consciousness but a person also must be conscious of being conscious.

Finally, both in philosophy and in everyday language, people often refer to other concepts of person such as legal persons or persons understood as characters in a theater play, or as personalities with specific features of character. There are reasons to believe that all criteria of persons mentioned above have serious philosophical shortcomings. In this part of the class, I provide you with the main gist of each of these conceptions and share with you the reasons why these conceptions are unable to provide a final definition of persons.

Rationality and self-consciousness
Definitions of persons based on criteria of rationality and of self-consciousness emerged as philosophers tried to answer the question, what particular feature makes a person distinct from other objects in the world.

Consciousness as a private feature
We have already seen that every criterion referring to consciousness relates to persons as each of persons can see herself from the inside. In this sense each person tastes her own sweetness of sugar and bitterness of lemon, feels her own pains and pleasures, hears and sees things from her own first-person point of view. Others may try to figure out how sweet things taste to me, but to do this they are unable to feel my taste of some honey; instead, they must refer to their own experience tasting sweet things and presume that my senses bring me an experience similar to theirs.

As Nagel emphasizes [see his article What Is It Like to Be a Bat in Hofstadter's anthology], consciousness or awareness is a phenomenon that each of us may access only from the first-person perspective. On the other hand self-consciousness is supposedly a public feature. This means that in principle we could test, from the outside, whether John is conscious of his consciousness or not. We may for instance refer to John's behavior.

However, criterion of self-consciousness has lost much of its appeal when it has been observed that many people exhibit no particular conscious reflection about their being conscious. Many philosophically less inclined individuals just go about their business and fail to reflect about their consciousness. It would be very odd to claim that they are not persons just because of this feature of character. Hence the criterion of self-consciousness is overly demanding.

Rationality as a public feature
Unlike consciousness, rationality is a public feature. We can devise certain criteria and say that one needs to be able to perform certain intellectual tasks in order to be rational.

The Turing test
There seems to be a problem with definition of persons based on rationality. If rationality is to be defined as a certain way of processing information, then it seems that computers would satisfy this definition at least as well as some people. In 1998 a super-computer called Deep Blue consistently won against Gary Kasparow, the world chess champion. In the light of this fact, it seems clear that that computers think. Moreover, in some areas computers think at least as well as human beings. Let me construct a short argument to demonstrate this point.

First we demonstrate that at least one computer can think:
1. It was clear that Deep Blue played chess. [One attractive option for our opponent is to say that Deep Blue was only retrieving information given to it by the programmers. But this is wrong since the programmers (separately or even collectively, as a team) would not have been able to play the game as well as Deep Blue. Hence, deep blue played the game.]
2. Playing chess well is an instance of thinking. [If playing sophisticated chess does not involve thinking then what does?] So everything that plays chess in a sophisticated way thinks.
3. Therefore Deep Blue thinks when playing chess.
4. Deep Blue is a computer. Hence, at least one computer can think.

Now we need to show that, in certain domain, a computer can think better than a human being. This is an easy argument to make:
5. Gary Kasparow is the world chess champion. He wins with other human players consistently.
6. Winning with a chess player consistently demonstrates that one is a better player. Hence, Kasparow is the best human chess player.
7. Deep Blue wins against Kasparow (and other human players). Therefore, at present Deep Blue is a better chess player than any human player.

Finally, we need to show that in some areas of thinking computers are better than humans:
8. We know from steps 3-4 that a computer thinks when playing chess. We also know from 7 that at present Deep Blue is a better chess player than any human. Therefore, Deep Blue's thinking in the area of chess exceeds that of any living human being.

This way I have proven that a computer can exceed a human being in a certain domain of thinking, namely in chess playing. We also know that computers can be much faster and more accurate in performing mathematical operations and other kinds of data processing than any human beings.

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