While cats, once toilet-trained, know how to use the toilet, what they don't know, like some of us, is how to flush it afterwards.
In general, as far as cats are concerned, unless rigorously trained, like circus cats, the whole world was a toilet unless otherwise instructed one way or the other, a behavior commonly observed in human society where for a certain segment of the population, the whole world was (i) a public spitoon or (ii) a public rubbish bin, except in public-behavior-strictly-policed places like Singapore, and in places like India, (iii) a public urinal as well.
