Students of tarot and astrology tend to take for granted the underlying influence of the four classical elements formulated by the Greek philosopher Empedocles – Fire, Water, Air and Earth – on the tarot suits and zodiacal signs. At their simplest, they represent action, initiative, enterprise and ego (Fire); emotions (Water); thoughts and ideas (Air); and all matters of a purely practical nature (Earth). Empedocles postulated the existence of two countervailing forces – Strife and Love – that create dynamic tension between the polar opposites, Fire/Water and Air/Earth, and unite elements of a sympathetic nature, Fire/Air and Water/Earth.
But a more complex blending of the elements is offered by the concept of elemental “humours.” Here is a lucid Wikipedia article on the subject and an extracted diagram showing the interplay between the factors of hot, dry, cold and wet:
These humours were brought to bear on the early diagnosis of medical conditions and the analysis of character traits according to four types of “temperament:” Choleric (Fire, hot and dry); Sanguine (Air, warm and moist); Phlegmatic (Water, cool and moist); and Melancholic (Earth, cold and dry). Note that I’ve taken some liberties with the model by applying a measure of shading to the impact of the elemental qualities: the introduction of wetness moderates the heat of Air, which is thus tempered to a condition of “warm and moist,” while Water is subject to both the warming influence of Air and the chilling effect of Earth, producing a “cool and moist” emphasis. In seasonal terms, the upshot could be akin to a soothing vernal mist or a chilly autumnal fog.
I came to these considerations while trying to plug the seven traditional planets into this model. For example, Venus – ruling Taurus and Libra – is an Earth and Air planet that partakes of both cold and warmth, and is considered “temperate” by James Wilson in his 1880 Dictionary of Astrology. Jupiter is a Fire and Water planet – ruling Sagittarius and Pisces – with a warm and moist nature that also falls in the temperate range, although slightly cooler than Venus according to Wilson. For his part, in Christian Astrology William Lilly deemed Venus to be “temperately cold and moist,” while he views Jupiter as “temperately hot and moist,” seeming to disagree with Wilson on the degree of warmth present in each case. Modern astronomers have determined that Venus is the hottest planet in the solar system, while Jupiter is frigid, but of course that has nothing to do with astrological interpretation. Here is the graphic presentation of the planetary array according to humour that I created for this purpose, and that basically follows Lilly. I haven’t examined it recently in light of my evolving appreciation for the classical elements, so it should be considered provisional at this point.