Another talk today by Peter Lumsdaine, this time all about weak ω-categories and -groupoids. A lot of the material was familiar, but it was like listening to a beautifully familiar story for the millionth time. There was a bit at the end that was new to me, though, talking about topological operads, and contractibility. An algebra for the trivial topological operad (where the space of n-ary operations is a single point, for every n) is just a topological monoid, but if each space of operations is contractible, then we have accomplished some sort of weakening of the definition to a "weak monoid".