Authority and testimony

Definition

Authority reasoning accepts a claim because a credible source vouches for it. Most of what anyone knows arrives this way, and it is perfectly good reasoning — as strong as the source's expertise in the relevant domain, their track record and incentives, and the agreement of other qualified sources.

Memory hook

“Trust the source as far as their expertise reaches — and no farther.”

What it sounds like

• According to the surveyor…
• She's spent forty years on exactly this.
• Every reference work agrees on the point.