In what sense is rank-based taxonomy an objective attempt to characterize a truth of the natural universe, and in what sense is it based on subjective decisions by the people doing the classification?

Answer 1

The objective characterization of rank-based taxonomy attempts to categorize organisms by grouping them by common characteristics that would be commonly recognized by anyone. The subjective nature of rank-based taxonomy is the classification system itself. There are numerous ways to categorize, so not everyone would come up with the same type of taxonomy structure.

Objective: Vertebrates - Grouping organisms that have or don't have a backbone. People could sort organisms objectively based on whether or not they have a backbone.

Subjective: Instead of categorizing by backbone, someone might decide to group organisms by the presence or absence of tails.

Answer 2

While previous classification was often based on relatively subjective criteria, today biologists are in the process of reclassifying living things on the basis of rRNA sequences. Since all living things have rRNA this provides an objective classification scheme.