I think I've featured thistles before, but I came across this picture lurking in a file I hadn't used for a while. The file comprised my photos of the gardens attached to the Madama Palazza in Turin - one of my favourite spots to hide away. Visitors are quite likely to miss these gardens in favour of palace exhibits, so it can be very peaceful there. You can see how closely related are thistles and artichokes. In fact, the artichoke is derived from a variety of thistle. They are prickly plants and central to the legend of the Scottish army being fortuitously disturbed by advancing Norse invaders - who stood on them. I don't know if that's true, but it would certainly be a painful experience. Symbolically, the thistle defends the heart. Nemo me impune lacessit - no-one touches me unharmed! It set me wondering about conflict - and the tendency these days to discourage critical expression. We just don't want to allow the prickles to prick us, so anything we say must pass through a neutralising filter. And if we don't do it for ourselves, then surely someone will do it for us. I had the privilege of hearing Augusta Boal, founder of the Theatre of the Oppressed, before he passed on. In a riveting lecture in London's ICA, he elaborated the concept of the "cop in the head". We are all encouraged to have this censor, he argued. In maintaining it, we immunise ourselves against exclusion and injustice. So I think we need our critical prickles so that we may better stay aware. If it moves, prick it.