eye of the beholder
The subjective appreciation or evaluation made by an individual viewer, participant, appraiser, etc. From the proverb "Beauty is in the eye of the beholder" (i.e., an approximation of beauty will differ greatly between different people). It's only in the eye of the beholder that such a nebulous thing as "truth" or "justice" has any real meaning. You may not like my new jacket, but style is in the eye of the beholder.