Antonyms of passion :
amiability, leniency, mildness, peacefulness, charity, lenity, patience, self-control, forbearance, long-suffering, peace, self-restraint, gentleness, love, peaceableness, allergy, animosity, antagonism, antipathy, aversion, disfavor, dislike, enmity, hostility, abhorrence, disgust, repugnance, repulsion, revulsion, misanthropy, abomination, hate, hatred, loathing, rancor, averseness, disinclination, disliking, distaste, nausea, apathy, indifference, insouciance, nonchalance, unconcern, insensitiveness, insensitivity, unfeelingness, aloofness, calmness, collectedness, composure, detachedness, dryness, phlegm, reserve, reservedness, reticence, taciturnity, stoicism, stoniness, stiffness, woodenness, chilliness, coldness, coolness, frigidity, frigidness, impassiveness, impassivity, insensibility, insensibleness, abstinence, celibacy, chastity.
Examples of usage:
Mary flew into a fine passion. "The Secret Garden", Frances Hodgson Burnett.
As to how much they may mean, perhaps the best way for those of our day to realize it is to take the example of Oberammergau with its great Passion Play still given. "Education: How Old The New", James J. Walsh.
Call it desire, passion- what you will! "The Splendid Folly", Margaret Pedler.