<P> Although the atomism of Epicurus had fallen out of favor in the centuries of Scholasticism, a related Aristotelian concept, that of minima naturalia (natural minima) received extensive consideration . Minima naturalia were theorized by Aristotle as the smallest parts into which a homogeneous natural substance (e.g., flesh, bone, or wood) could be divided and still retain its essential character . Speculation on minima naturalia provided philosophical background for the mechanistic philosophy of early modern thinkers such as Descartes, and for the alchemical works of Geber and Daniel Sennert, who in turn influenced the corpuscularian alchemist Robert Boyle, one of the founders of modern chemistry . </P> <P> Unlike the atomism of Leucippus, Democritus, and Epicurus, and also unlike the later atomic theory of John Dalton, the Aristotelian natural minimum was not conceptualized as physically indivisible--"atomic" in the contemporary sense . Instead, the concept was rooted in Aristotle's hylomorphic worldview, which held that every physical thing is a compound of matter (Greek hyle) and an immaterial substantial form (Greek morphe) that imparts its essential nature and structure . For instance, a rubber ball for a hylomorphist like Aristotle would be rubber (matter) structured by spherical shape (form). </P> <P> Aristotle's intuition was that there is some smallest size beyond which matter could no longer be structured as flesh, or bone, or wood, or some other such organic substance that for Aristotle, living before the microscope, could be considered homogeneous . For instance, if flesh were divided beyond its natural minimum, what would be left might be a large amount of the element water, and smaller amounts of the other elements . But whatever water or other elements were left, they would no longer have the "nature" of flesh: in hylomorphic terms, they would no longer be matter structured by the form of flesh; instead the remaining water, e.g., would be matter structured by the form of water, not the form of flesh . This is suggestive of modern chemistry, in which, e.g., a bar of gold can be continually divided until one has a single atom of gold, but further division yields only subatomic particles (electrons, quarks, etc .) which are no longer "gold ." However, the parallel is not exact: minima naturalia are not a direct anticipation of modern chemical and physical concepts . </P> <P> A chief theme in late Roman and Scholastic commentary on this concept is reconciling minima naturalia with the general Aristotelian principle of infinite divisibility . Commentators like John Philoponus and Thomas Aquinas reconciled these aspects of Aristotle's thought by distinguishing between mathematical and "natural" divisibility . With few exceptions, much of the curriculum in the universities of Europe was based on such Aristotelianism for most of the Middle Ages (Kargon 1966). Scholasticism was standard science in the time of Isaac Newton, but in the 17th century, a renewed interest in Epicurean atomism and corpuscularianism as a hybrid or an alternative to Aristotelian physics had begun to mount outside the classroom . </P>

Who proposed that all matter is composed of indivisible particles called atoms