Since UFO stands for unidentified flying object, the word ufology means approximately knowledge about unknown flying objects, and is therefore a science whose content is void by definition. Similar considerations hold for parapsychology.

Many scholars have felt that the Heronian passage [on a pipe-organ moved by an anemourion-like wheel] can be disregarded because it is not confirmed by other writings. Heron presumably mentioned the anemourion in a moment of distraction, forgetting that it had not been invented yet. We know that he was given to such lapses.

Today Eratosthenes' method [of calculating the circumference of the earth] seems almost banal... yet it is inaccessible to prescientific civilizations, and in all of Antiquity not a single Latin author succeeded in stating it coherently.

The oft-heard comment that Leonardo [da Vinci]'s genius managed to transcend the culture of his time is amply justified. But his was not a science-fiction voyage into the future as much as a plunge into the past.

From semantics to shipbuilding, from dream theory to propositional logic, any specialist ... is invariably astonished to discover that modern knowledge was foreshadowed at the time. ... Should we not replace these foreshadowings by the study of the influences of Hellenistic thought on modern thought?