The ordinary and already old notion of a "space of time "
is meant as a determination of time by itself and only of time. It does not mean, as does the word time-space, that grounding essence which is originarily unified with respect to time and space.
"Space of time" means a span of "time," the "from now until then," the "from then up to today," etc. We speak of a "space of time" one hundred years in length. Time is represented here as spacious, inasmuch as it, qua measure-number, encompasses something, a from ... up to ... , something measured. What is meant here is thus not even metaphorically that open realm of time which pertains to its ecstases and which is obviously not "spatial." Represented in the term "space of time" is therefore also the ordinary concept of "time."
An elucidation of time-space could be expected from a consideration of the history of the representations of space and time.
Yet all those historiological accounts, attempted in all sorts of ways since the nineteenth century, are blind, useless, and bereft of any actuaL philosophizing question, not to mention the fact that they merely pick out and string together "passages" in which some problem or other is discussed.
The history of the "representations" of space and time is the history of the truth of beyng and can be exhibited in a philosophically fruitful way only if joined to the history of the guiding question. Everything else is erudite pretence which merely leads further astray into the superficiality of gathering and comparing passages
242. Time-space as the abyssal ground
The abyssal ground [Ab-grund] is the originary essential occurrence of the ground [Grund]. The ground is the essence of truth. If time-space is thus grasped as abyssal ground, and, reciprocally, if the abyssal ground is grasped more determinately by way of time-space, then the turning relation and the belonging of time-space to the essence of truth are thereby opened up.
The abyss is the originary unity of space and time, that unifying unity which first allows them to diverge into their separateness.
Yet the abyssal ground is also, and primarily, the originary essence of the ground, of its grounding, of the essence of truth.
What is the abyssal ground? What is its mode of grounding? The abyssal ground is the staying away of the ground