The etcs tag has no wiki summary.

**2**

votes

**1**answer

202 views

### Can we define geometric morphisms (between ETCS categories) elementarily?

The ETCS axioms give conditions on a category for it to be a category of sets. These axioms can be written out in first order language, resulting in a finite axiomatisation of the category of sets. ...

**6**

votes

**1**answer

344 views

### How do we compare models of ETCS?

The elementary theory of the category of sets (nLab) gives axioms on a category such that it is a category of sets. In answering this MO question I realised that we might have trouble comparing ...