Asked by: Sue Hiett, Leighton Buzzard
For those who believe in the soul, the question of its location has a perennial interest. The ancient Egyptians thought that it was found in the heart, and tomb pictures from around 2000BCE (before the common era) show the god Anubis weighing the soul-laden heart against the Feather of Truth. In 1515 Leonardo da Vinci was denounced as a sorcerer for attempting to find the soul by dissecting the brain, following the belief of the time that it existed in the centre of the head.
Some believers claim that the soul is an insubstantial entity (derisively labelled by Cambridge philosopher Gilbert Ryle as 'the ghost in the machine'), but this begs the classic philosophical question how an insubstantial entity can ever affect a material body. American doctor Duncan MacDougall concluded from this that the soul, if it exists, must have weight, and in 1907 reported experiments where he measured the change in weight of dying tuberculosis patients. His answer, encapsulated in a later film title, was that the soul weighed 21g. Make of that what you will.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
