A writer describes gradually losing language

A writer’s memoir of a brain tumor slowly destroying his ability to use language

When I came to read this passage “…floating and flailing weightlessly.…” I said the word “weightlessly” as “walterkly”. It took quite a bit of effort to be fully sure that this was a mistake; and more effort and repeating to grasp what exactly this nonsense word was, to establish its sound – I had to construct it phoneme by phoneme – clearly enough to write it down. And it seems that the reading eye, darting backwards and forwards, was plucking letters from the whole vicinity, and mixing them up, having lost its usual ability to sort them.What the whole thing emphasises, of course, is how what we call self-command is really a matter of having reliable automatic mechanisms, unthinking habits or instincts.