He had by then fired his brain, and was navigating on the advice of his soul alone…
The narrator sees humanity’s “great big brains” as an evolutionary mistake, as founts of pointless angst and pain and self-destruction. And so he tells the tale of us evolving into less intellectual, non-tool-using, seal-like creatures as a story of nature retreating from insanity into a more reasonable state of affairs. It’s not a viewpoint that I find easy to dismiss, though I like to think the jury is still out.
Vonnegut’s writing is delightful, though by revealing the end as well as all major details early in the book, he does make the last part a bit dull.