The number of genes in the operon containing the gene considered (No. of genes in operon), gene essentiality (Essential), COG membership, the cellular distribution of the gene product, the presence of a peptide signal in the mRNA and the nature of the second nucleotide in the mRNA (Nature of 2nd nt) were considered as qualitative parameters.
So one option for biological essentialism is to drop the traditional view that the natural properties that are essential for membership of a natural kind are intrinsic: natural, extrinsic (relational) properties can play this role (Okasha 2002).
Even as a nonagenarian, Dr. Cooley remains a poster boy for this cohort, possessing all the qualities essential for membership: a distaste for conventional wisdom, a disregard of limits, a lack of pretension commensurate with a lack of fear.
Three attributes were essential for membership in the Ottoman ruling class: profession of loyalty to the sultan and his state; acceptance and practice of Islam and its underlying system of thought and action; and knowledge and practice of the complicated system of customs, behaviour, and language known as the Ottoman Way.
The members of Canis familaris, for example, tend to share a number of common properties (having four legs, two eyes, and so on), but given the forces of evolution, no biological property is essential for membership in that species.
Biologists explain the characters of organisms by citing other characters, without the added metaphysical claim that a character cited in an explanans is essential for membership in a taxon.
Billions of marketing dollars per year are directed at making consumer stuff essential to membership in our consumer culture.
The two kinds of essentialisms are also often treated as co-dependent: if some feature is essential for class membership, then this feature must also be essential to individual members of that class qua individuals.
By contrast, Philip Gordon, America's undersecretary of state for Europe, had called Britain's EU membership "essential and critical to the United States".
The third question asks whether there are properties that might be essential for kind membership.
