In a magnificent letter of 1932, to McGreevy, Beckett had chastised one of his own poems for being facultatif, or optional. It did not, he said, "represent a necessity." These letters are a quest for necessity, "for what must be written about, at whatever cost."
Read the whole thing here. "More and more my language appears to me like a veil which one has to tear apart in order to get to those things (or the nothingness) lying behind it."