|The three elements of nature, according to Heraclitus: earth, water, and fire, aka the three element theory.|
The three element theory was introduced by Greek philosopher Heraclitus, in circa 500BC, supposedly derived in some way from the Egyptian Heliopolis creation myth, according to which the universe resulted from a primordial abyss from which fire (Ra) burst forth thereafter self-engendering earth (Geb) and water (Nun). 
In c.450BC, Empedocles added "air" to the previous three elements, therein making the four element theory.
● Two principles
● Three principles
1. Luckert, Karl. (1991). Egyptian Light and Hebrew Fire: Theological and Philosophical Roots of Christendom in Evolutionary Perspective (§:Heraclitus, pgs. 206-). SUNY Press.
● Kahn, Charles H. (1981). The Art and Thought of Heraclitus: a New Arrangement and Translation of the Fragments with Literary and Philosophical Commentary (three-element theory, pg. 154). Cambridge University Press.