Hello, I am wondering what resources are most helpful in learning the progress made by category and topos theorists in creating a "new" foundation for mathematics. So far I have: Categories for the Working Mathematician Topoi by Goldblatt First-Order Categorical Logic by Makkai An Introduction to Higher-Order Categorical Logic by Lambek After learning from these books, where would I go to learn about the mathematical applications and framework supplied by topos theory? Uh-oh... This should be in General Math, not General Physics. Can someone move it?