Maybe each human being lives in a unique world, a private world different from those inhabited and experienced by all other humans. . . 

If reality differs from person to person, can we speak of reality singular, or shouldn't we really be talking about plural realities? 

And if there are plural realities, are some more true (more real) than others? 

What about the world of a schizophrenic? 

Maybe it's as real as our world. 

Maybe we cannot say that we are in touch with reality and he is not, but should instead say, His reality is so different from ours that he can't explain his to us, and we can't explain ours to him. 

The problem, then, is that if subjective worlds are experienced too differently, there occurs a breakdown in communication 

... and there is the real illness.