Hi there Leigh! I have a kind of random question. What does "like calls to like" mean? Looking forward to siege and storm!

From Shadow and Bone:

The grounding principle of the Small Science was “like calls to like”, but then it got complicated. Odinakovost was the “thisness” of a thing that made it the same as everything else. Etovost was the “thatness” of a thing that made it different from everything else. Odinakovost connected Grisha to the world, but it was etovost that gave them an affinity for something like air, or blood, or in my case, light.

So let’s say that Odinakovost is the essence that all things share. But Etovost is the unique quality that makes a thing itself and nothing else. A Grisha needs a fundamental understanding of both of these properties in order to manipulate matter.

It is Etovost, that unique quality, that determines which types of matter a given Grisha can manipulate—something within that Grisha shares the same unique quality, recognizes it, is attracted to it. Basically, “like calls to like” speaks to this attraction.

(The inspiration came from a verrrry loose interpretation of quiddity and haecceity, and the idea of molecular “preference” in chemistry.)