In the Magic Book there is the knowledge tree. The knowledge tree shows all available knowledge in a way that goes from the beginning to the end, from elementary to more complex. All knowledge starts with four elements, Fire Water Earth and Air.
In some other traditions and variations of this one there are 5 elements, with fifth one being aether, void or space. Japan also has the 4 plus another 2, making 6 elements. The other two are Aether (as quintessence, life force and lightning) and Nether (dark, deadly and shadows). The Chinese classical elements are also 5, they are, however, different – Wood, Fire, Earth, Water and Metal.
Fire
One of the four basic forms of existence and origins of knowledge. Magical form of energy, movement, reaction, change, transformation. Some symbols for fire that have been used:
Classical Greek symbols dominate the four elements. The last two are Kenaz Rune (from Runic divination system) and Fire Trigram from I Ching.
Fire is very beautiful. It is also elusive. What's especially cool about it is that one can create Fire out of non-fire. Firemaking is one of the basic skills of humans and is important for survival. It is also important for magician who wishes to control fire. Fire is alchemical process of Combustion. One of the elements that Fire produces is water.
Water
One of the four basic forms of existence and origins of knowledge. Magical form of flow, fluid, reflection, transition and emotion. Some symbols used:
Here, the second symbol is Celtic symbol for water. Also notice the I Ching trigram is reversed compared to the fire trigram. To the left the trigram is Laguz rune symbolizing water or lake.
Water doesn't disappear like fire, it goes through all the 4 states of matter and remains itself. Water can store/carry energy or effect put on it by the magician. Because water doesn't disappear, the effect can be multiplied over time (through continuous practice). Water is very important in Alchemy, for example in Purification (purifying water) and Separation (Electrolysis). If fire may be the most basic Process (Combustion), then water should be the most basic Substrance.
Air
One of the four basic forms of existence and origins of knowledge. Magical form of space, spirit, breath, infinity, invisibility. Some symbols that have been used:
The swirls are similar for water and air, I tend to imagine air to be more curly like a smoke coming off. Air is usually preferred element for magician interested in knowledge, mysticism, mind or spiritual. The corresponding meditation would be concentration on breathing.
Earth
One of the four basic forms of existence and origins of knowledge. Magical form of matter, form, terra, world, nature. Some symbols:
Earth is the foundation and from where we stand all other elements stand on top of that foundation. Earth is natural, folk and craft magic, closely related to nature and the natural world. For example, Earth magician is more likely to seek or find a familiar, communicate with nature and spirits of nature (like in Shinto).
Here's another interesting version of glyphs for the 4 elements based on their elemental energies made by the Order of Aether:
Magic System and Elemental Cards
I have 2 main roles in the system that the 4 elements hold. For one, each element opens a piece of knowledge in the Knowledge Tree, the four elements being the first 4 pieces of knowledge that are available to the magician. The second is elemental cards, which are constructed similarly to Tarot cards but for purpose of practicing magic and not for divination.