鉴别器 - Chinese Dictionary

He was absolutely uncritical and believed everything.

There can be no differentiation without contrast.

differential diagnosis

ability to differentiate; power of discrimination; discernment

discriminate the sham/false from the genuine

discriminate counterfeit bills from genuine money

discern between right and wrong; distinguish right from wrong

distinguish the good from the bad; distinguish between the good and the bad

make an appraisal of antiques; appraise antiques