Why is "Son of Man" by Rene Magritte considered a masterpiece?

Coming late in his career, painted in 1964, the Son of Man could be said to be the quintessential Magritte painting. It is a self-portrait which examines a theme that was central to the whole of Magritte's work, namely the fickleness or treachery of images. The painting deals with the visible and the obscured, the iconic and the mundane.

Magritte was a surrealist. His intended goal for his work was to challenge observers' preconditioned perceptions of reality and force viewers to become hypersensitive to their surroundings. Unlike other surrealists, like Dali, who invoked the use of dream imagery and the unconscious as inspiration for their images, Magritte used startling juxtapositions of everyday objects in bizarre relationships to emphasise his points. So we have ordinary man, ordinary suit, ordinary apple, ordinary landscape arranged in an extraordinary relationship to highlight what is most important, which is the faulty meanings we ascribe in the unthinking act of seeing.

This painting forces us to "look twice" and to question what it is we see. I think it is quite brilliant.

Because no one before could express what he did