Writing is not the last step of thinking, it's the mechanism of thinking

Ahrens's foundational claim upends a common assumption: that we first think clearly and then write the thought down as a record. He argues the sequence runs the other way — clarity is mostly a product of the act of writing, not a precondition for it. Vague impressions and half-formed hunches only become precise, testable ideas once you're forced to put them into complete sentences that someone else (or your future self) could understand without the surrounding context in your head.

This is why he's skeptical of people who claim to have a fully formed argument "in their head" that they just haven't gotten around to writing yet. Usually what's in the head is a feeling of understanding, not an actual argument, and that feeling evaporates under the scrutiny that writing demands. Notes and drafts aren't a record of thinking that already happened elsewhere; they are the site where the thinking actually occurs.

Takeaway: don't wait to "figure it out" before writing — write badly and specifically, and let the writing itself expose what you don't yet understand.