By Schubert Ogden
The Notebooks of Schubert Ogden
Hartshorne speaks of "individuals, on no matter what level (particle, atom, cell, vertebrate, human)" ("Freedom as Universal [1996]": 2). Elsewhere in the same essay, he refers to "the singular level of animal, cell, molecule, atom, particle, etc."---evidently meaning by "the singular level" simply "the level of singulars," which is thus synonymous with "the level of individuals" (7).
Putting the two passages together, one may say that, on Hartshorne's account, there are at least the following distinguishable levels of individuals or singulars, reading from the lowest to the highest:
particle atom molecule cell animal vertebrate human
September 1997