All three of our artists today have attempted something completely and utterly new. Duchamp, initially inspired by the complexity of cubism and the driving energy of futurism, tried to change the art world by exhibiting objects he hadn’t made and in so doing, created a new form of art as a result – the “readymade”. Dalí changed our expectations in different ways, by subverting our perception through unlikely confrontations of form – but like Duchamp, he invited us to see familiar objects in different ways. Rachel Whiteread, on the other hand, is effectively the opposite of Duchamp. Rather than presenting us with readymade objects, she shows us forgotten spaces, voids we never see and would not consider, giving life to the gaps behind books and under the bath, and creating echoes of uninhabited rooms. She reminds us of the power of the objects we do not see and leads us to imagine the lives of those now gone. The first two artists are brought together this autumn in an unexpected and groundbreaking exhibition at the Royal Academy, whist the third will be enjoying a major retrospective at Tate Britain. When considered together they will help us to consider what is – or for that matter isn’t – necessary to make a work of art.