Aristotle's contribution to the understanding of atoms was to help dispel the commonly held belief of his time that the indivisible building blocks of matter were uniform in nature and had no unique or characteristic properties. He argued that the atoms of a specific substance must instead maintain the unique properties of that substance rather than all atoms remaining similar in nature. Aristotle also noted that some substances appeared to be pure and that others were formed from the combinations of these pure substances, an observation which led to the understanding that elements could be combined to form compounds with new and unique properties.
The focus of Aristotle's attention regarding what was to develop into the field of chemistry was the nature of matter and its various transformations. He recorded his many theories and observations in what are now considered to be some of the first scientific treatises on chemistry, biology and physics.
Although Aristotle's 4th-century B.C. speculations on atoms, elements and compounds were based on a relatively narrow range of physical observations and assumptions, he created the philosophical foundation for those who were to follow. He was correct in believing that new substances could be created by the interactions between others. Aristotle also correctly noted that heterogeneous substances could be reduced to their component parts, such as saltwater being reducible to its individual components of water and salt.