In various belief systems, four is considered an earthly number, there being four elements. Water, Air, Fire, and Earth. Three is considered a divine number, and there are three qualities: Cardinal, Fixed, and Mutable. Three plus four equals seven, the number often signifying the union of heaven and earth and the deliverance of people.

Three Qualities
The Qualities assign the Signs into Quadruplicities, three groups of four. They are occasionally referred to as crosses because each quality forms a cross when drawn across the zodiac. Christian astrology relates the three qualities to the three aspects of God in the trinity.

• Cardinal signs (Aries, Cancer, Libra and Capricorn) are associated with initiation, creativity and leadership.
• Fixed signs (Taurus, Leo, Scorpio and Aquarius) are associated with stabilization, determination, depth and persistence.
• Mutable signs (Gemini,Virgo, Sagittarius and Pisces) are associated with adaptability, service-providing and expansion.