Well, apologies to all concerned for taking so long to post this, but here it is. The Categorically Not! two Sundays ago was -as usual- extremely enjoyable and informative. This one was all about Illusion, in some sense, the theme being "Really?".
We started out with a few opening remarks by Bob Miller, who specialises in what some might call "light art". He's well known for creating a large number of wonderful works using light and shadow, several of them forming the cornerstone of exhibitions in the Exploratorium in San Francisco, for example. Have a look at the "lightwalk", linked here.