The most fundamental concept of science is that of atomic matter. As far back as the fifth century BC, Greek philosophers were recorded as having considered the possibility of matter being composed of fundamental indivisible particles, called atoms.

Leucippus of Miletus conceived of a world composed of atoms within voids. His protégé, Democritus of Abder, refined his mentor's concept. Democritus theorised atoms as immutable, indivisible building blocks of many varieties, whose fundamental natures accounted for the properties of matter. These ideas were confined to a small circle of esoteric thinkers, and were forgotten, during the Roman era and the Dark Ages that followed. As late as 1910, the American chemist Alexander Smith stated that 'the handy way in which the atomic hypothesis lends itself to representation of the characteristic features of chemical change falls short of constituting proof that atoms have any real existence'.

Secondary school science students are now routinely taught about atoms, about the periodic table, and about the valence shell electron pair repulsion theory of electron pairing and atomic bonding, as dogmatically as they were taught the alphabet in early primary school. Students are lucky if a teacher makes mention of the history of atomic theory at all, to give them some appreciation of how hard fought the development of atomic and molecular science was. With the first experiments with, and applications of, atomic fission in the 1940s; and current-day scanning electron images of the atoms of metals, in neat rows, with different-sized atoms of other elements interposed upon the surface to read messages; there hardly seems the need.

Picture if, despite the brilliant discoveries in astronomy and physics in the Renaissance and in the age of Enlightenment, scientists of the era neglected giving any thought to matter at a minute level. Chemical and mineral properties of matter would have been haphazardly catalogued, and observed reactions would have been little better than a cookbook for inedible substances. Explanations of matter would have remained in the realm of the 'fundamental' phases - as earth, water, wind and fire, with a bit of ether here and there, to fill the gaps.

The reactions of matter would likely continue to be explained in nebulous, metaphysical terms, and many alchemists would be toiling to this day, attempting to convert lead or tin into gold. Any scientific development of chemistry, metallurgy, or medicine would be unthinkable, to say nothing of nuclear physics. We would still be citizens of the seventeenth century.