Strength is an Old Energy Archetype from the Masonic Tarot Deck. In the Book of Slavery and Book of Power, the archetype is used to equate strength with domination, illustrated visually by the women's domination of a lion, representing nature.
List of Old Energy Archetypes from the Masonic Tarot
Chariot, Death (archetype), Hermit, Hierophant, High Priestess, Judgement, Justice, Star, Strength, Sun (archetype), Temperance, The Devil, The Emperor, The Empress, The Fool, The Hanged Man, The Lovers, The Magician, The Moon, The Tower, The Wheel of Fortune, The World (old energy)
Book of Power
Self-explanatory. Trials, testing, tribulation built strength. Fool in School
(the Strength; the brother who has become strong through mastering his own person.) Trial by Fire exteriorizes inner heat.
"Now consider Strength.... The picture shows a woman taming a lion. Briefly, the image suggests the energy of the unconscious released and calmed, 'tamed' by the direction of conscious understanding." "passions conquered by reason." (p. 76).
Subduing the self: "(Strength) maintains the balance between desire and will." 
Assumption that humans have a "dark side" which must be controlled by higher reason "This also represents the mastery of the lower by the higher. But in this case it is the soul which holds in check the passions, although her feet are still planted on earth, and the dark veil still floats about her head and clings around her."
Book of Slavery
"By making Strength number 8 we set it against the Chariot, as a different kind of power, not the ego's will, but the inner Strength to confront yourself calmly and without fear. The mysteries can be brought out because we have found the Strength to face them. The lion signifies all the feelings, fears, desires, and confusions sup pressed by the ego in its attempt to control life. The charioteer drew upon his inner feelings as a source of energy, but was always careful to direct that energy where he consciously decided it should go. Strength allows the inner passions to emerge, as the first step in going beyond the ego....On a deeper level the lion symbolizes the whole force of personality, usually smoothed over by the demands of civilized life...This purpose can only be accomplished because the lion is 'tamed' at the same time that it is released.. 
Just note the intellectual contortions Pollack is going through to make this a sensible and progressive archetype.
- Wirth, Oswald. Tarot of the Magicians: The Occult Symbols of the Major Arcana That Inspired Modern Tarot. San Francisco. CA: Weiser Books, 1990. p. 171.
- Pollack, Rachel. Seventy-Eight Degrees of Wisdom. Harper Collins, 1980.
- Case, Paul Foster. An Introduction to the Study of the Tarot. New York: Kindle Edition, 1920. p.30.
- Wang, Robert. An Introduction to the Golden Dawn Tarot. Main: Sam Weiser, 1978. p. 138.
- Pollack, Rachel. Seventy-Eight Degrees of Wisdom. Harper Collins, 1980 p. 74.
[Is related to::Fool in School| ]]