This seems to me to be part of the debate about Universals, and especially about Abstract nouns. An Essence which is universal, unchanging,and indivisible, is distinct from an
Accidental like colour, position, size which is variable, inconstant and can be divided up.
quia materia non est per se sufficiens ad individuandum,
Because matter is not in itself sufficient for (having indivisibility) [better] individuatation
dicitur quod conditiones quaedam materiae et accidentia individui,
it is said that certain states of matter, and (certain) accidents of an indivisible thing,
sicut esse hic et esse nun, individuant, a quibus abstrahit ration
such as here-ness and now-ness, are indivisible, from which the Universal concept abstracted.
The last four words are untranslatable: the easiest solution would be to read rationes universalis as accusative plural: 'from which he has derived the universal concepts,' or '...the universal principles.'