By and large, logicians who came after Avicenna adopted many of his assumptions and distinctions: his understanding of the absolute proposition (at least with respect to the modalization of its predicate), the wasfî/dhâtî distinction, the division of the syllogistic into repetitive and connective. They worried, however, about a number of his claims concerning modal propositions and the productive syllogisms that can be built from them. By the middle of the thirteenth century, a primary concern was about finding truth-conditions for propositions that could be useful for the sciences (see Text 24 below), though everyone started from Avicenna's formulations. A central distinction in these later discussions was between externalist and essentialist readings of the propositions. This is what the terms “externalist” and “essentialist” mean: