Locke's memory theory
The main point
A person is a thinking, conscious being at a moment in time. To be the same person over time is to extend one's consciousness over time, such that one is conscious of past experiences much as one is conscious of present experiences. Section 9 is very important.
Personal identity is thus distinct from of either the identity an animal body (that's a man, according to Locke) or the identity of any substance, whether material or immaterial. This is what Locke most wanted to show: the independence of personal identity from the identity of substances.
Necessary and sufficient conditions
In arguing for his position, Locke asks his readers to consider imaginary cases in which consciousness (and memory) apparently comes apart from body or soul. The thought experiment is born! We didn't go over these in a lot of detail in class but you should feel comfortable with them nonetheless.
Here's what Locke maintains: A is the same person as B iff A is conscious of B's experiences. That involves both a necessary and a sufficient condition of A's being the same person as B.
The sufficient condition: "If A remembers B's experiences, then A is the same person as B" or, in other words, "A's remembering B's experiences is a sufficient condition of A's being the same person as B."
The necessary condition: "If A and B are the same person, then A remembers B's experiences" or, in other words, "A's remembering B's experiences is a necessary condition of A's being the same person as B."
Locke's opponents make similar claims. For example:
Same soul as a sufficient condition of personal identity: "If A and B have the same immaterial substance or soul, then A and B are the same person."
Same soul as a necessary condition of personal identity: "If A and B have different immaterial substances or souls, then A and B are different persons."
Do you recall how the material conditional works from logic? If not, that's no big deal. Material conditionals (if ... then statements, as above) are false in only one way: when the antecedent (the "if") is true and the consequent ("then") is false. So if you want to show that a given material conditional is false, try to show that it's possible for the antecedent to be true and the consequent to be false.
When is the claim "if Y, then X" false? When you have a Y but no X.
When is the claim "if X, then Y" false? When you have an X but no Y.
How do Locke's examples fit this pattern?
How might one object to Locke's theory, following this pattern?
You should be able to think of examples without consulting your notes. If you can't, you need to study these points.
About that talking parrot ...
A relation we have in a newspaper of great note, is sufficient to countenance the supposition of a rational parrot. Its words are:
"A Thinking Bird or Just Another Birdbrain?"
"Calm down," Alex, an African Gray parrot, told Dr. Irene Pepperberg, the scientist at the University of Arizona who owns him. "Don't tell me to calm down," Dr. Pepperberg snapped. Sometimes Dr. Pepperberg and Alex squabble like an old married couple. He even says, "I love you."
For the last 22 years, Dr. Pepperberg has been teaching Alex, who is 23, to do complex tasks of the sort that only a few nonhuman species -- chimpanzees, for instance -- have been able to perform. But unlike those other creatures, Alex can talk, or at least, he can vocalize. And, Dr. Pepperberg says, Alex doesn't just imitate human speech, as other parrots do -- Alex can think. His actions are not just an instinctive response, she says, but rather a result of reasoning and choice.
Source: Dinita Smith, "A Thinking Bird or Just Another Birdbrain?" The New York Times, October 9, 1999, Section A; Page 1; Column 4
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