In Cameron Shaw’s most recent show, his assisted readymades, inspired by Duchamp and Magritte, seemed to levitate. The artist’s carefully selected commonplace objects defied gravity with the help of well-placed magnets, in work that toyed with the psychology of perception while revealing the tricks of the artist as self-styled magician. Among the nine such works were a fakir’s rope ascending to the sky, a black derby floating in a vitrine, cigars and pipes suspended from strings, and a quill pen that appeared to write a letter (in which a son describes his father’s death to his brother) by