Rupert Read argues that irrationality cannot be understood, that we cannot make sense of nonsense. If someone is schizophrenic, therefore, we should not expect to be able to understand them. I think he would allow that we might be able to understand them and/or things they say some of the time, but he also writes that "sometimes the closest we can get to understanding (for example) schizophrenia [is] becoming clear that it is not understandable." And he does not mean only the illness but the people who suffer from it and (some of) the things they say because of, or out of, it.
This strikes me as being true in two ways. Trivially, if someone talks nonsense because of a mental illness (or for any other reason) then this is nonsense and its meaning cannot be understood because it does not exist. If it did it wouldn't be nonsense. More interestingly, there is something condescending about claiming to understand anyone else too much, and it seems as though such claims are always at least in danger of being too much when the someone else is schizophrenic. There must be something seriously alien about their thinking for them to be rightly diagnosed as schizophrenic.
But it also seems false in some ways too. If I have had schizophrenia but am currently OK, whether or not because of medication, couldn't I reasonably claim to understand the illness? (I don't mean that such claims are bound to be reasonable, only that it seems some could be.) Or if I work with a schizophrenic person all the time, might I not have some understanding of him? At times this understanding might be of the fairly minimal that's-just-what-he-does-when-there's-thunder variety, but then that's only different in degree from our understanding of anyone, isn't it? It's the kind of understanding that we have of animals, after all, and we are animals ourselves. I think Read would accept all this.
Another criticism that I think people sometimes want to make of Read's view is that, while avoiding belittling schizophrenics, it instead rejects the very possibility of a human relationship with them at all. They are alien, after all, and incomprehensible. This criticism is probably unfair. I'm sure it is aimed at something he does not mean.
But a different kind of criticism is also possible, and I think Coetzee at least gestures toward this. (This link isn't much help, but it's the paper I'm talking about.) Read wants to say that there is something we cannot do, even if we are as gifted as can be when it comes to thinking or writing or understanding. There is something, in particular, that writers cannot do. Or at least he seems to want to say this, although he also says that he agrees with almost everything Coetzee says in response to him. Perhaps his choice of words is sometimes misleading and that's all there is to it.
Rather than say things like "there is no understanding schizophrenia because there is nothing there to understand" (which is the kind of thing Read says about solipsism, and he relates solipsism to schizophrenia often), Coetzee seems to want to say that there could be something called "understanding schizophrenia." I'm tempted to say that Read rejects these words as having no meaning while Coetzee out-Cora Diamond's him by saying they haven't been given a meaning yet, until someone (perhaps Faulkner) comes along and gives these words meaning. But I'll resist saying that until I've re-read Read's original paper and The Sound and the Fury.