Earth, Water, Fire and Air
The phylosofers of the old Greek sciences tried to understand and explain Nature. The introduces the concept "element".
Aristoteles said: there are four elements:
er zijn vier elementen: Earth, Water, Fire and Air. All substances are built up of these four.
Thus: wood must contain a lot of the element Fire, becaus, when burning, lots of Fire comes out. That makes sense, isn't it?
Later, in the Middle Ages, the alchemists continued this way of thinking and joined water and earth toghether: 'Mercure'. Air and Fire were joint to the element 'Sulphur'. They tried - in search of the right composition of these two, to make Gold.
These are phases in the development of science. Every phase contributed.