It is evident that I have consciousness. How can I prove that there are other minds besides mine, then? If I cannot prove the existence of alter ego, must I accept solipsism?
1. Solipsism bothers philosophers
Suppose you are seeing an animation movie on TV. You are identifying with the hero of the movie and weeping over a loss of his sweetheart. However, when you come round, you notice that all the story and characters of the movie were fictitious and what you had seen was just an image projected on the screen.
Let’s apply this experience to the entire world. Suspect a friend you are talking merrily to is a phantom like an animation character of TV. Unlike characters of television, the friend replies to your question, to be sure, but on interactive TV, you cannot make out whether you are communicating with a person or a computer.
You can doubt anything. Nagai, who wrote this article, might be just a mindless writing machine. The media that are supposed to tell you the experience of other people have deceived you and the fact is that you are the only conscious being…
No ordinary people would think of such a thing. However, philosophers are queer species and some of them continue worrying about this problem throughout their life.
2. The Analogy theory
In order to refute solipsism, the following analogy theory is often appealed to. For example, we can understand toothache of others by such analogy:
I have toothache.
I behave in a certain way, when I have toothache.
Somebody behaves in the way.
He must have toothache.
The analogy theory infers other minds, just as we infer x=6 from the relation 1:3=2:x.
I have two questions to this analogy theory.
First, is the existence of alter ego no more evident than an answer of a mathematical problem, while that of ego is evident?
Second, does understanding other minds mean to experience, think and behave in the same way as theirs?
My answer to them is no.
3. Alter ego reflects other possibilities of Ego
Needless to say, the analogy theory does not assert that to understand alter ego we must have the very toothache alter ego has. What they insist is that we should be able to infer that alter ego would have the same kind of toothache as mine. Even so, however, do the beings that experience, think and behave in the same way as mine deserve the name of other minds?
You do not regard your faithful subordinates, for example, as others. Just as your arm, which moves as you order, is part of your body and not alter ego, your faithful subordinates, who move as you order, are not others but part of organization as an enlarged body.
Alter ego is an agent who can select otherwise than I select. It is not until the faithful subordinates show a sign of betrayal that they can be others. A similar phenomenon can be found in a personal body. When corpus callosum that bridges both hemispheric brains is cut off, the mind of the patient is divided into two, each of which moves parts under its control.
It is because we can waver that we are conscious beings. A conscious being sometimes hesitates to select any action and does nothing, but to do nothing is also a result of decision. So, the conscious being always selects a certain alternative and excludes the other. As a mind as an information system is nothing but selection, there can always be another mind in myself. This possible alter ego is as evident as ego. In wavering, ego has communicated with alter ego.
Of course, the actual alter ego is different from this possible alter ego. Though alter ego in general is as evident as ego, it is not evident what specific motive makes alter ego behave in a specific way. I must infer the motive from external behavior. Here those who try to refute solipsism get anguished, saying, "There always remains indeterminacy in understanding alter ego, because it depends on indirect inference."
Let’s solve the problem in a reversed way. I cannot completely understand alter ego. There always remains indefinite opacity in other minds and the behavior of alter ego is unpredictable and uncontrollable, but this is the very reason that other minds deserve their name. If I know completely all the motives of an agent and can control it at will, it is no longer alter ego but part of my body.
4. Uncertainty refutes solipsism
Trying to prove the existence of alter ego is comical, when you come to think of it. To prove something is to show that it is necessary and has no other possibility, namely to delete otherness. An ambiguous analogy is enough to understand other minds.
Mechanical determinism and idealistic solipsism stemmed from the common paradigm of modern philosophy: lack of otherness. If you accept the ontology of indeterminacy, which I advocate, you can see ego without alter ego is as absurd as consciousness that never wavers in selection.