The Guardian's Notes and Queries tells me that cats are crepuscular (what a wonderful word). This means they are very active in the twilight hours, morning and evening, when they can pounce gleefully on little defenceless creatures who can't see the cats as well as the cats can see them.
I couldn't agree more, especially when it means they take up several chairs whilst sleeping off their dusky activities - you'll notice the "don't even think about it!" sideways glance!
though perhaps this studied indifference is even more cutting - "your chair ... whatever makes you think that?"