Fifty Years of Categorical Logic

Andrei Rodin and I organized a special session on Categorical Logic as part of Universal Logic 3. We also organized a special issue of Logica Universalis on the same theme. As it turns out, 2013 is the 50th anniversary of Bill Lawvere's Columbia phd thesis, possibly the best birthdate for categorical logic. So we decided to call our preface for the special issue "Elements of Categorical Logic: Fifty Years Later".

Here is this preface.