To be precise, the heart symbol with a line through it's base-point, stood for VITRIOL, which was a mnemonic for a secret latin sentence in which each word began with a letter that stood for each one of the seven psychic educating processes (Visita Interiora Terrae Rectificando Invenies Occulta Lapidem). These 'coded' words signified what we would understand as the alchemical educating process: Incubation, Dichotomy, Catharsis, Rectification, Synthesis, Sublimation, and Transmutation. The quitessence of the process was the fifth stage known as the 'Mysterium Coniunctionem' or Synthesis. This was often identified by a reddening (losis). Hence, the RED HEART could stand for the quintessence of learning or coming together in Synthesis like lovers.

In the Christian religion, Red can be an emblem of passion, but more especially the blood of martyrdom, as of St Valentine, who was bludgeoned and beheaded for not renouncing his Christian fatih in 270 of the Christian Era. Red was laid down as symbolising the blood and passion of Christ and of martyrdom in the 13th century Roman Missal (tit, xviii) and by Pope Innocent III in the 11th century in his holy book De Sacro Altaris Mysterio.