"impartial" in the adjective sense
1. impartial
showing lack of favoritism
"the cold neutrality of an impartial judge"
2. unprejudiced, impartial
free from undue bias or preconceived opinions
"an unprejudiced appraisal of the pros and cons"
"the impartial eye of a scientist"
Source: WordNet® (An amazing lexical database of English)
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