In 1667, Johann Joachim Becher published his book , which contained the first instance of what would become the phlogiston theory. In his book, Becher eliminated fire and air from the classical element model and replaced them with three forms of the earth: , , and .   was the element that imparted oily, sulphurous, or combustible properties. Becher believed that  was a key feature of combustion and was released when combustible substances were burned. Becher did not have much to do with phlogiston theory as we know it now, but he had a large influence on his student Stahl. Bechers main contribution was the start of the theory itself, however much of it was changed after him. Bechers idea was that combustible substances contain an ignitable matter, the .