 Avicenna also originally puts his own distinction between the referential/substantial and descriptional reading to use in his theory of science. Each of the above two types of necessity (essential and non-essential) can hold on either reading. In particular, the descriptional reading, which Avicenna takes to be the default sense of necessity in scientific discourse, allows us to study the properties of a given object qua object of a certain kind (a bronze triangle qua triangle) and to make true, necessary predications about it as long as it is a triangle (but not as long as it exists, as a bronze triangle could be re-cast into a different shape and lose some of the properties that necessarily hold of it qua triangle) (Strobino 2015a).