At left we see the 1573 version of his Summer, one of a series of portrayals of men made up of natural objects, in this case representing the seasons. The fruits and veggies (including an eggplant, yikes!) are beautifully rendered, the colors are warm, and the "face" is smiling, but the effect is not reassuring.
I've thought about the discomfort caused by his productions and have come to this conclusion. The history of the West is ostensibly one of rationality, and the cornerstone of Western rationality is the law of non-contradiction, or tertium non datur. Something either is or is not x. A thing, or a person, is one thing only, and we can perceive and understand (and thus control) that thing.
But Arcimboldo's work suggests that this is not so. Is this one subject or many? Is this a human or a bunch of fruits and vegetables? More subversively: do humans have an immortal soul or are they just a part of waning nature, deceptively florid as in the summer, but headed toward decay and nothingness?
Some have noted that Arcimboldo was a precursor of Gestalt psychology. Think of the famous vase that also looks like two profiles.
Arcimboldo had already done this sort of thing (again, with a man and veggies):
After his initial fame, the artist was forgotten until he was adopted in the twentieth century by the Surrealists, particularly Salvador Dali'. Contemporary Western society with its World Wars and monstrous political phenomena brought out the irrationality at the heart of our culture, which was already foreshadowed by the seemingly minor artist Arcimboldo.