The statement of a law of nature involves the formation of a concept, or general idea, in which the likenesses of phenomena are collected, and the di… - J. R. Partington

The first clear expression of the idea of an element occurs in the teachings of the Greek philosophers. ...Aristotle ...who summarized the theories of earlier thinkers, developed the view that all substances were made of a primary matter... On this, different forms could be impressed... so the idea of the transmutation of the elements arose. Aristotle's elements are really fundamental properties of matter... hotness, coldness, moistness, and dryness. By combining these in pairs, he obtained what are called the four elements, fire, air, earth and water... a fifth, immaterial, one was added, which appears in later writings as the quintessence. This corresponds with the ether. The elements were supposed to settle out naturally into the earth (below), water (the oceans), air (the atmosphere), fire and ether (the sky and heavenly bodies).

It is necessary to guard against a possible danger... of submitting too readily to the result of a so-called "crucial experiment". Very few experiments can, in the nature of things, be really crucial. One so-called "crucial experiment" which decided between Newton's corpuscular theory of light and Huyghens' wave-theory, viz. the relation between the law of refraction and the velocity of light, was not at all decisive.

The earliest chemical theory was qualitative in the strictest sense; the so-called Aristotelean doctrine of the four elements assumed that air, water, earth, and fire, were qualities impressed on a primal matter; and the changes of material bodies were explained by the assumption that properties could be taken up by, and impressed upon, or removed from, the base-stuff. Transmutation as a possibility followed at once, and centuries of vain endeavour were required to impress the fact of its impossibility, leading to the true concept of element.