Sentence:  But, it being evident that things are ranked under names into sorts or species, only as they agree to certain abstract ideas, to which we have annexed those names, the essence of each genus, or sort, comes to be nothing but that abstract idea which the general, or <WSD>sortal</WSD> (if I may have leave so to call it from sort, as I do general from genus), name stands for. 
Meaning of the word marked with <WSD> tags:  Of or pertaining to a sort, or kind.