The Common Principles of Natural Philosophy

and accidental form, just as Aristotleoriginal: "Aristoteles"; the 4th-century BCE Greek philosopher whose works formed the basis of medieval science. teaches in the 7th book of the Metaphysicsoriginal: "Methaphisice"; Aristotle's treatise on the fundamental nature of reality and being.. This is the true matter from which all other modes of matter are named, whether in natural or artificial things; and thus "matter" is understood most especially in the usage of the 4 b 2. metaphysicians. In a third way, matter is said to be that 5 which is in potentialityoriginal: "potencia"; the capacity of a thing to become something else or to reach a more complete state. toward something else, as if toward its completion; just as the essence of a genusoriginal: "generis"; a broad category or class of things (e.g., "animal"). is in potentiality toward a specific differenceoriginal: "differenciam specificam"; the particular characteristic that distinguishes a species from others in the same genus (e.g., "rationality" distinguishes humans within the genus "animal")., and an embryo is potentially a child, and a child is potentially a man, and universally everything incomplete in respect to its completion; and thus "matter" is taken in the usage most 10 especially of the natural philosophers. By them, it is called the "subject" in generation and corruptionoriginal: "generacione et corrupcione"; the process of coming into being and passing away., which is common to two opposites being transmuted within it; for the generation of one opposite is the corruption of the other. These opposites are two species regarding something common to them, or two individuals of two species regarding a third thing common 15 to them. Now, nothing is immediately common to two species except the essence of the proximate genusoriginal: "generis proximi"; the most immediate category above a species (e.g., "bird" is the proximate genus for a "robin")., and nothing is common to two individuals of two species except the individual of the genus; as "animal" is common to a rational animal and an irrational animal, and "this animal" is common to 20 "this rational [one]" and "this irrational [one]," and "heavy" is common to earth and air, and "this heavy [thing]" is common to this earth and this air.

Therefore, natural matter in the generation and corruption of species is the incomplete essence of the proximate genus, which is born to be completed by the species; and natural matter in 25 the generation of individuals is the incomplete essence of the individual of the genus, which is born to be completed by the individuals of the species. This matter, in the generation of species, always possesses one of them, just as the essence of the genus in earth possesses the specific nature of earth; and when an opposing agent, such as water or the power of the 30 heavens which can produce water, acts upon the earth, it destroys the specific matter of the earth down to the essence of the genus—which is common to both water and earth—and from that incomplete essence it produces water; whence that...