Aristotle's basic conception of substance is directly interwoven in his explanation of the scientist and his projection of the methods that are appropriate for use in the sciences. He argued that the objects studied in the physical sciences have natures (274) or internal principles of motion that determine inorganic, organic, and psychological change. Change and art are distinguished from nature as external principles of change, one with and one therefore without intelligent planning. The field of physics limits its scope of inquiry to the connections of things with the processes and properties based on their natures. Metaphysics, in contrast, is concerned in Aristotle's (275) philosophy with being as being, the necessity of differentiating from what is contributed by the mind, the manner of speech in inquiry into being, and also of separating that which is essential to the conception of statement of truth from what conception and statement are true of. That which is most truly in existence therefore is substance.
Aristotle (274) stated that "there are three kinds of substance - one that is sensible (of which one subdivision is eternal and another is perishable) [...] and another that is immovable and the third kind belongs to another science." Sensible substance in his view is changeable and therefore may not necessarily be predictable. What does not change in his view is the Prime Mover or the First Cause. The Prime Mover is an eternal unmovable substance that may have caused the changeable substances of destructible existing things to have come into being (281).
Substance is not to be equated solely with matter. Matter in the Aristotelian formula is a relative term and refers to those things found in nature as well as those things made of natural substances. Aristotle made reference to the various elements (i.e., earth, water, fire, and air) in discussing matter and substance, moving from matter to form and f...