Mine's on pg 348. 1997 edition. Mac Lane's is on pg 106 (2nd edition). It would 
be interesting to know whether the choice(s) were made to introduce the concept 
earlier later based on the trajectory of the text or the intuitive naturalness 
of the concept. Oddly, I like the definition Mac Lane gives in the Appendix (pg 
289) better than the one on pg 106. But I don't really understand any of it. 
I've placed Jon's 2 youtube recommendations in The Queue.

On 7/9/20 9:49 AM, Jon Zingale wrote:
> Ha, yeah. They spend much of the book developing categories that are
> simultaneously rich enough to be topos-theoretically interesting and simple
> enough to reason about their properties/consequences. Recently, another
> friam member got me thinking about locales[Ɏ], the toy categories presented
> by Lawvere and Schanuel have been helpful to me in reasoning about them.
> 
> [Ɏ] From https://ncatlab.org/nlab/show/locale: A locale is, intuitively,
> like a topological space that may or may not have enough points (or even any
> points at all).


On 7/9/20 9:26 AM, Frank Wimberly wrote:
> Did you realize that Lawvere doesn't define the term "topos" until page 352?


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