Aristotle's main contribution to chemistry consists of the first systematic treatise on the field which he wrote in the 4th century B.C.E. His treatise built on earlier work by the Greek philosopher Empedocles (450 B.C.E.) and Democritus (420 B.C.E.)
Empedocles postulated that all things were made up of four essential elements: earth, fire, air and water. Democritus' theory - that all matter was made up of tiny substances eternal in nature that cling together - gave rise to atomic theory.
Aristotle added to both theories on the nature of matter by stating that the exact nature of each specific type of matter came about because of the infinite possible variations of hot/cold/moist/dry in combination with the four elements earth, air, water and fire.