While taking a pee into Brown's cornfield, Roland's paranoia takes over a bit. He realizes that the Man in Black has drawn him here, had wanted him to stop and visit with Brown. This epiphany leads him to wonder whether or not Brown is actually the Man in Black himself in disguise.
He quickly discounts this notion as pointless and needlessly upsetting thoughts. To think in this way would be flirting with insanity, with someone completely off the deep end, and the "only contingency he had not learned how to bear was the possibility of his own madness."
Why does Roland fear madness in himself? Is it because he's sub-consciously aware that the seeds have been planted, sown, and are ripe for the reaping? Does he feel that madness would prevent him from completing his mission?
I think that maybe madness is necessary for Roland's completion of his mission. Any thoughts?