With one of the world's most controversial thinkers on hand, Monday night's Q&A was bound to offer some curly conundrums. And so it was that Peter Singer came to the panel offering guidance on the following; how many slices of cake to eat at a kid's birthday party; guide dogs - good or bad?; and a diverting final debate that could really keep you up nights - should the courts grant human rights to chimpanzees?

Between the dogs and the chimps, another animal-related question lurked unasked - was Q&A finally jumping the shark? - but in the context of the debates it all sort of made sense, even if you were wondering why everyone avoided the elephant in the room, Singer's far more confronting opinions on mercy killing of the severely disabled.

But for Monday night's purposes, the renowned ethicist's thoughts on the wisdom of funding guide dogs for the blind were probably provocative enough. In a debate over the best way to spend one's charitable dollar, Singer mounted what in a philosopher's lecture hall would sound an impeccably logical case but which may have played less well in suburban living rooms.

In essence, he suggested that the costs of funding guide-dog training in the wealthy west compared to the cost of donating to save someone in a developing country from becoming blind in the first place made the latter a better use of your charity buck. "It's a matter of getting the best value for your money," Singer said. 'What's better - to prevent someone becoming blind or give a dog to a blind person?"