The photic sneeze effect has been documented for many centuries. The Greek philosopher Aristotle was one of the first to contemplate this strange phenomenon in 350 BCE, exploring why looking at the sun causes a person to sneeze in The Book of Problems: "Why does the heat of the sun provoke sneezing?" He hypothesized that the sun's heat caused sweating inside the nose, which triggered a sneeze in order to remove the moisture. In the 17th century, English philosopher Francis Bacon disproved Aristotle's theory by facing the sun with his eyes closed, which did not elicit the ordinary sneeze response. Bacon therefore guessed that the eyes played a vital part in triggering photic sneezing. He assumed that looking at the sun's light made the eyes water, and then that moisture proceeded to seep into the nose and irritate it, causing a sneeze. Although plausible, scientists later determined this theory to also be incorrect because sun-induced sneezing occurs too quickly after sunlight exposure; watering of the eyes is a slower process, so it could not play a vital part in triggering the reflex.