## May 14, 2021

### Structure vs. Observation

#### Posted by Emily Riehl

*guest post by Stelios Tsampas and Amin Karamlou*

Today we’ll be talking about the theory of universal algebra, and its less well-known counterpart of universal coalgebra. We’ll try to convince you that these two frameworks provide us with suitable tools for studying a fundamental duality that arises between *structure* and *behaviour*. Rather than jumping straight into the mathematical details we’ll start with a few motivating examples that arise in the setting of functional programming. We’ll talk more about the mathematics at play behind the scenes in the second half of this post.