Thumb

The thumb is the digit the planetary scheme does not fit. The four fingers take their names from the mounts at their bases and carry them consistently across the whole literature, from the twelfth-century Latin chiromantia through Johannes ab Indagine's printed handbook of 1522 to the French system of the nineteenth century: Jupiter under the index, Saturn under the middle, Apollo under the ring, Mercury under the little finger. The thumb has no planetary finger-name of its own. What it has instead is the largest mount in the palm sitting at its base, the Mount of Venus, and the lower Mount of Mars just above it inside the curve of the life line, so that two planets are attached to one digit from below rather than one from above.

The tradition compensates by reading the thumb harder than it reads any finger. Cheiro treats it apart from the planetary scheme and divides it in two: the first phalanx, the one carrying the nail, is read for will, and the second for reason, with a long and firm thumb taken for resolution and a short or soft one for the want of it. Reading the shape of the hand and its digits in this way is chirognomy, the half of the subject that Casimir Stanislas d'Arpentigny set out in La Chirognomonie in 1843, as against chiromancy, the reading of the lines, which Adolphe Desbarrolles systematised in 1859. None of it has been shown to work. The associations are traditional and interpretive, and the accuracy readers report is well accounted for by cold reading.

Sources Introductiones apotelesmaticae elegantes in chyromantiam, physiognomiam, astrologiam naturalem, complexiones hominum, naturas planetarumJohannes ab Indagine (Johannes Rosenbach) with Palmistry for AllCheiro (William John Warner), La Chirognomonie, ou l'art de reconnaitre les tendances de l'intelligence d'apres les formes de la mainCasimir Stanislas d'Arpentigny, Les Mysteres de la MainAdolphe Desbarrolles

Outside the Western scheme the thumb is not read, it is used, and the two great elemental hand systems of Asia disagree about what it stands for. In the esoteric Buddhism recorded in Japanese sculpture the five fingers are the five elements counted inward from the little finger: earth, water, fire, wind, and at the thumb space or the void, ku, the element that contains the rest. In the yogic hasta mudras the assignment runs differently and the thumb is fire, agni, the element the other four are brought to touch. The two schemes agree about exactly one digit, the index, and the thumb is the plainest of their disagreements: the container in one reckoning, the igniter in the other.

Both readings lean on something the hand actually does. The thumb is the only digit that opposes, swinging across the palm to meet each fingertip in turn on a saddle joint at its base that no other digit has, and it is the only one with two bones where the rest have three. A gesture that joins thumb to fingertip is therefore available in a way that no finger-to-finger contact is, which is why the seal formed by touching thumb to index is the commonest in the whole repertoire, and why both elemental schemes make the thumb the fixed term and the fingers the variable one. The anatomy does not confirm the symbolism. It does explain why the symbolism was built around this digit rather than another.

Sources Mudra: A Study of Symbolic Gestures in Japanese Buddhist SculptureE. Dale Saunders with Asana Pranayama Mudra BandhaSwami Satyananda Saraswati