Simultaneousness is often confounded with presence and with co-existence. But these three notions, rigorously speaking, differ from one another. _Presence_ refers to terms in space; _simultaneousness_ to terms in duration; _co-existence_ to terms both present and simultaneous. Thus presence and simultaneousness are the constituents of co-existence. Presence is to be considered as the material constituent, because it depends on the “where,” which belongs to the thing on account of its matter or potency; simultaneousness must be considered as the formal constituent, because it depends on the “when,” which belongs to the thing on account of its act or of its resulting actuality. Before we proceed further, we must yet remark that in the same manner as the infinite virtuality of divine immensity receives distinct extrinsic denominations from the contingent terms existing in space, and is thus said to imply _distinct virtualities_, so also the infinite virtuality of God’s eternity can be said to imply distinct virtualities, owing to the distinct denominations it receives from distinct terms of contingent duration. It is for this reason that we can speak of virtualities of eternity in the plural. Thus when we point out the first instant of any movement as distinct from any following instant, we consider the flowing of the contingent “when” from _before_ to _after_ as a passage from one to another virtuality of standing duration. These virtualities, however, are not distinct as to their absolute beings, but only as to their extrinsic termination and denomination; and therefore they are really but one infinite virtuality. As all that we have said of the virtualities of absolute space in one of our past articles equally applies to the virtualities of absolute duration, we need not dwell here any longer on this point.