An independent impression is a belief formed through a process that excludes epistemic deference to the beliefs of others. Independent impressions may be contrasted with all-things-considered beliefs, which are beliefs that do allow for such deference.
The concept of an independent impression appears to have originated in a comment by user Rolf Nelson on the Overcoming Bias blog, back when it was still a group blog prior to the formation of LessWrong. Nelson lamented the "lack of generally-accepted terminology" to express the concept of "the opinion of each person, before they factored in the opinions of the others." Hal Finney then published a post on that blog recognizing the importance of the concept identified by Nelson—which Finney paraphrased as "beliefs we would have had if we didn’t choose to be persuaded by the fact that everyone else believes differently"—and invited readers to suggest a name for it. Eliezer Yudkowsky suggested "independent impression" and Anna Salamon and others seconded that suggestion, though no clear consensus emerged; other proposals included "independent belief" (Hanson), "first impression" (Hanson), "initial thought" (Yudkowsky) and "uncorrected impression" (Yudkowsky).
In 2009, Salamon and Steve Rayhawk published a post on LessWrong discussing possible epistemic practices conducive to the spread of accurate beliefs within the rationality community. One of the practices proposed was "to explicitly separate 'individual impressions' (impressions based only on evidence we’ve ourselves verified) from 'beliefs' (which include evidence from others’ impressions)." In a comment, Robin Hanson singled out the value of this particular proposal, but raised the worry that "we actually have a whole range of indirection […] If I actually looked something up recently in an encyclopedia, while someone else just vaguely remembers looking it up sometime long ago, is that my impression or my belief?"
In the following years, there was very limited use or discussion of the concept of an independent impression. Activity appears to have resumed only around 2017, after Katja Grace published a number of posts applying the distinction. At around that same time, some authors independently came up with equivalent distinctions. For example, in a post about epistemic modesty, Gregory Lewis distinguished between "credence by my lights" and "credence all things considered", which as noted by Claire Zabel corresponds to "independent impressions" and "all-things-considered beliefs", respectively....