There are many tools used in Modern Witchcraft. According to some Wiccan systems, the first four are not physical, but rather are qualities which must be developed within the witch.
The "Four Pillars of the Witches Temple" are;
To Know (nescere)
-corresponds to Air
-represents the witch's reason/intellect/intuition/wisdom and other more mystical understandings...
Basically this has to do with the gaining of knowledge, whether it be from books, teachers, or from experience. This also includes anything having to do with organising said knowledge: remembering, analyzing, dissecting, logical reasoning, imagining, linking, and many more. This is shown in many kinds of knowledge needed to do ritual: from remembering the words to invocations, to knowing when to cast the circle, to knowing what incense to use, to remembering how it feels when one grounds correctly.
In witchcraft knowledge is power. No knowledge is ever wasted, and you may find that your fifth grade Creative Writing class taught you things useable for creating invocations, or that your Aunt Jean's gardening tips are helping you with your herb growing, or your Tai Chi class helped get the idea of centering across.
The admonitions "Know Thyself", "Know your Craft", "Learn" and "Apply you Learning" are all included in the pillar.
To Will (velle)
-corresponds to Fire
-represents the witch's Will/Discipline/her skills in the arts of magic and life.
This can be split into two categories: the mundane and the Magickal. The mundane is where a with tries to keep their life in good order, and to follow through on promises and commitments. The magickal version refers to the Will to see a spell or ritual to its completion, keeping the intent clear without letting onself get distracted.
Concentration, Discipline and Drive are definitely a part of this, as well as Enthusiasm for doing ritual in the first place.
Placing one's will in tandem with Divine Will is also incuded.
"Keep you thoughts and deeds in good order" and "Breathe and Eat correctly" belong here (though really just the act of living up to all the Goals could be listed inder "To Will")
To Dare (audere)
-corresponds to Water
-represents the witch's Emotions/Heart since the word courage derives from a word that means "heart"
"To Dar" encompasses the acts of facing fears, especially with regards to doing magick. Dare to experiment with what one has learned to gain more experience, like trying out that new astral travel technique or trance working. Dare to meet the Gods and interacte with them. Dare to deal with inner darkness.
This is not to say that one must never feel fear. Fear must be felt and examined before it can be dealt with. The more one tries to hide one's fear from one's self, the more power that fear will have over one's self. Facing the Shadow within can be more traumatic than facing the most awe-inspiring Deity. However, Starhawk mentions in her book The Spiral Dance, "Where there's fear, there's power." One's greatest fear can mask one's greatest strength.
It must be stated that any emotion or personal attribute brought into a magickal circle will be increased and strengthened. This explains the admonition at the gateway "Better to fall upon this knife/Than enter here in fear, or strife". Give strength to your courage.
To Keep [the] Silence (tacere)
-corresponds with Earth
"To Keep the Silence" is often interpreted as "To Keep Silent": that is, to keep secret knowledge of witchcraft, of membership and places of meetings etc., except in cases of voucher-for persons. "To Keep Silent" is probably a good general practice since it keeps the foolhardy from trying things that might be dangerous or from getting flack from less sympathetic neighbours. This is, however, not the whole story.
"Silence" represents the 'still point'... the silence within... The correspondence with Earth here also gives another hint of this interpretation, since in order to begin to work magick, we generally "ground" and "center" ourselves. It is difficult to keep clear one's intent if other extraneous thoughts keep flitting by and being distracting.
Listening to the Gods and Nature (and other people for that matter) is also intimated since one cannot hear unless there is silence first.
Again, "Keeping your thoughts in good order" as well as "Meditate" come under this heading
To Go (ire)
-corresponds to Spirit
Some traditions use the fifth Element of Spirit as embodying the power "To Go": to go forth, to journey, to make manifest, to evolove. Most traditions assign Spirit to the Gods, making spirit a combination of the other four elements in perfect balance.
If one sees each of these qualities written on a four-sided pyramid, "To Keep the Silence" would be on the base, with the other three (To Know, To Will, To Dare) rising from the base (ie. Earth, foundation) to meet at the top. All things begin and end in Silence.
All of these qualities must be developed to gain proficiency in magick. (Remember "Achieve Balance")
The Way of the Goddess by Ly Warren-Clarke
The Spiral Dance by Starhawk