I found it interesting that James basically admits that when considering the work of religious innovators (religious geniuses? what's the right term?), we are dealing with people that we would ordinarily write off as unmedicated schizophrenics. That seems like a hard thing for us to accept, maybe even more so today than then.
"Let us play fair in this whole matter, and be quite candid with ourselves and with the facts. When we think certain states of mind superior to others, is it ever because of what we know concerning their organic antecedents? No! it is always for two entirely different reasons. It is either because we take an immediate delight in them; or else it is because we believe them to bring us good consequential fruits for life. When we speak disparagingly of 'feverish fancies,' surely the fever-process as such is not the ground of our disesteem *for aught we know to the contrary, 103° or 104° Fahrenheit might be a much more favorable temperature for truths to germinate and sprout in, than the more ordinary blood-heat of 97 or 98 degrees*. It is either the disagreeableness itself of the fancies, or their inability to bear the criticisms of the convalescent hour. When we praise the thoughts which health brings, health's peculiar chemical metabolisms have nothing to do with determining our judgment. We know in fact almost nothing about these metabolisms. It is the character of inner happiness in the thoughts which stamps them as good, or else their consistency with our other opinions and their serviceability for our needs, which make them pass for true in our esteem."