Check out the PARC Forum on September 18, 2008 Residual Categories: Silence, Absence and Being an Other
Residual categories (for example, none of the above; not elsewhere categorized; not otherwise specified [NOS]; other) are ubiquitous in all working classification systems. Where and how they appear, and are used, changes historically and politically. Their presence also reflects the nature of technical descriptions of nature: something always escapes formal description. This has been noted by thinkers including Gödel, Wittgenstein, Gregory Bateson, and John Dewey
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