The Elements and Correspondences.
Our world is viewed of in terms of four physical elements - earth, water, air and fire (which roughly correspond to the four scientific forms of matter: solid, liquid, gas and plasma) - plus spirit. Together, these elements form a united whole, as is symbolized in the pentagram. All are necessary and should be in balance.
Circles are generally cast through the use of all elements. Incense (fire and air) and salt water (earth and water) is the simplest method, with yourself representing spirit. Candles (fire), incense (air), water (water), and (especially if you're outdoors) the ground beneath your feet (earth) also work. The compass points of a circle each represent an element as well, with the circle itself being spirit, uniting and binding all together.
Each of these elements correspond to certain aspects, and when attempting to do work concerning a certain aspect, we address the appropriate element.
Air Celtic name: Airt
Direction: East
Time: Sunrise
Season: Spring
Moon: Waxing
Goddess: Maiden
Tools: Incense, Wand
Major Aspect: Intelligence
Air is the element of intellect, study, and book-learning, and therefore of the sciences. It is also the element of youth, creativity, and spontaneity, and of communication and travel.
Fire Celtic name: Deas
Direction: South
Time: Noon
Season: Summer
Moon: Full
Goddess: Motherhood
Tools: Candle, Athame
Major Aspect: Strength
Fire is the element of strength, especially physical strength but also strength of will, and energy. Fire is also the element of passion, courage, protection, purification, transformation, chaos, and sex. Fire is life and health as well as destruction.
Water Celtic name: Iar
Direction: West
Time: Sunset
Season: Autumn
Moon: Waning
Goddess: Crone
Tools: Chalice, Cauldron
Major Aspect: Wisdom
Water is the element of wisdom, clarity, and common sense, especially that which comes from experience. It is also the element of emotion, intuition and divination. It is the major element of healing, and also contains aspects of transformation and purification, and can also represent death and rebirth.
Earth Celtic name: Tuath
Direction: North
Time: Midnight
Season: Winter
Moon: New
Goddess: Dark
Tools: Salt, Pentacle
Major Aspect: Stability
Earth is the element of stability, order and grounding. It is also the element of fertility, both literal and figurative, and therefore of pregnancy, growth, birth, material gain, business, prosperity sustenance, and creativity. As the element from which came and to which we will return, earth is the element of death and rebirth, beginnings and endings, and silence.
Because earth symbolizes endings and beginnings, I cast my circles starting in the north.
SpiritAlso referred to as Ether or Aethyr.
Direction: Center and circumference
Tools: Circle, self
Major Aspect: Everything and nothing
Spirit is the element of transcendence, transformation, change, the void, everywhere and nowhere, all time and no time. It is the primal force that flows through all of us and all things. It is not often addressed directly in ritual, because it is the element of ourselves, our will, and the gods, all of which are already actively invoked.