Abstract
The stumbling block in human science, or, more specifically, the science of the mind and brain, is that the subjects that are directly observed are not "human beings", but "myself and others". Also, in the so-called "problem of qualia" too-"How are the qualia produced in the human brain?" I must set the problem differently according to the case of my own "brain and qualia" and that of another's "brain and qualia". First this paper describes a thought experiment about the brain-qualia relationship that is carried out within the strictly first-person perspective. As a result, I found that no causal relationship was observed between my brain and my qualia, and I realized that my brain is a part of my qualia but not vice versa. Next, I propose the problem of "other minds" as a really hard problem. My solution is in the idea of "possible worlds". Qualia of a certain other person (e.g. Mr. X) are my own qualia in the possible world where I was born as Mr. X. Lastly, the relationship between the actual world and possible worlds is discussed.
