The artist Félix Vallotton captured moral ambiguity and the shadows in human relationships like few others. A retrospective of his work has just opened in Amsterdamhat goes on behind the closed doors of outward respectability – from the suburban semi to the Elysée Palace – and the passions that seethe in the darker chambers of the human heart will always exert a powerful ­fascination. The artist Félix Vallotton (1865-1925), a retrospective of whose work has recently opened at Amsterdam’s Van Gogh Museum (until 1 June), explored and exposed many of the more disturbing aspects of the psychology of humankind – deception, ­violence, lust, hypocrisy and compromise – with a pictorial grace and meticulous technique that give their subjec