It was those very clever ancient Greeks who first asserted that the world was round. They arrived at this conclusion initially for purely philosophical reasons, proceeding with impeccable logic from two doubtful premises to a clear non sequitur: a sphere, they argued, is the perfect shape, and nature is perfection - so the Earth must be a perfect sphere. In due course, careful observation confirmed to their satisfaction both the quality of their aesthetic sensibilities and the precision of the syllogism they engendered.
Their conclusion on this matter has come to be shared by most of us in the intervening years - but not by all. Columbus, for example, had his doubts about this paradigm of Greek perfection, and St Augustine argued that if the world was round, those who lived on the wrong side would be unable to witness Christ's return in triumph on the Day of Judgment - a discrimination which, obviously, God would not allow.
The flat Earth lost another champion about a week ago. Charles K. Johnson, who died in California, was president of the Flat Earth Society for nearly 30 years, a body which, at its peak some decades ago, incorporated several thousand members.
Earth was to Johnson, and presumably still is to his surviving followers, a flat, circular disc floating in a vast continuum of primordial fluid. The North Pole lies at the centre of this disc, and the equator is a circle half way out; Antarctic ice forms a wall around its outer rim, and since no one has ever crossed this wall of ice, we have no idea whatever what may lie beyond.
The sun and moon, in this philosophy, are both about 30 miles in diameter, and circle above the Earth near the equator at a height of some 3,000 miles. The moon shines by its own light, and the apparent rising and setting of both bodies are tricks of perspective, like that which causes railway tracks to seem to meet near the horizon.
Johnson's personal beliefs were firmly grounded in the Bible, which contains many suggestions that the Earth is flat. In the New Testament, for example, Christ ascended up to heaven, and there is obviously no "up" or "down" in a universe comprising spheres. But apart altogether from the Bible, to Johnson the very idea of Australians hanging by their feet beneath a spheroid world was patently absurd.
"Wherever you find people with a reservoir of common sense," Charles Johnson said, "they don't believe in such idiotic nonsense as an Earth that spins around the sun. Reasonable, intelligent people," he maintained, "have always known the Earth is flat."