On Physics

On Rest. Chapter 10.

Having spoken of motion, we must speak of rest. For opposites placed next to each other shine forth more clearly A common medieval logical principle: contrasting two things makes their individual natures easier to understand.. Rest is defined thus: Rest is that which exists in a thing that has the capacity to be moved, yet is not currently being moved. From this it is clear that just as motion exists within time, so rest also exists within time. However, we do not intend to speak here of rest as it exists in God or in the angels. Also, according to Avicenna The Latinized name of Ibn Sina, a Persian polymath whose works on physics and medicine were foundational to medieval university learning., rest is the privation of motion in that which has the capacity to move, but is not moving. From this it is clear, as stated above, that just as motion is divided into natural, violent, and animate, so too is rest.

Natural rest is when a body is in its own proper place, determined for it by nature, such as the earth at the center or fire on high In the Aristotelian worldview, the element of Earth naturally seeks the center of the universe, while Fire naturally seeks the periphery.. Animate rest original: "quies animalis"; rest pertaining to living beings. is when the soul ceases from motion, whether it is joined to the object of its desire or not. Violent rest is when a body is in a place that is accidental to it, such as if earth were on high and fire were at the center.

On Place. Chapter 11.

Next follows the discussion on place. Place is defined by Damascenus John of Damascus, an 8th-century theologian whose work "The Orthodox Faith" was a major source for medieval physics and theology. thus: Place is the bodily boundary of that which contains, in accordance with how it contains that which is contained; for example, air contains the body, but the body is contained. Furthermore, place is twofold: namely, intelligible and sensible.

Intelligible place is the place of spiritual creatures, such as angels and departed souls; although they may be in a physical place, they are not there physically, but intelligibly, as Damascenus says. Indeed, an intelligible place is where it is understood to be; it is the intellectual and incorporeal nature where a thing surely exists and operates. Physical place is the place of bodies, which was defined above.

And note that a thing is said to be in a place in three ways: circumscriptively, definitively, and repletively.
1. A thing is said to be in a place circumscriptively when a beginning, middle, and end can be assigned to it in that place, or when its parts are measured by the parts of the place; this is how a physical body is in a place.
2. A thing is said to be in a place definitively when it is "here" in such a way that it is not "elsewhere"; this is how angels are in a place, for an angel is where it operates (as Damascenus says), as are departed souls. I say "departed" because souls united to a body are in the same place as their body.
3. A thing is said to be in a place repletively when it fills the place; in this way, God is in every place, for God fills every place.

Furthermore, some things are in a place through themselves original: "per se"; essentially or by their own nature. like a subject, while others are there by accident original: "per accidens"; incidentally, such as a color being in a place because the object it colors is in that place. like the qualities that exist within a subject. Also note that there is common place and proper place. A common place is like the heavens, of which Damascenus says: "The heaven is the container of visible and invisible creatures..."