The modern scientific world picture is ever refining the mathematical technical projection of inanimate nature, order as calculable and ordered relationality posited in advance.  Heidegger comments

Already in the last century, philosophy clearly recognized and spoke of the transformation of the concept of substance into the concept of function.  The actual is conceived as function subject to mathematical and technical calculability.  There is a functional nexus of actual effects in space and time.  The entirety of what is actual is a system of mutually dependent , functional changes of state a=f(b).  “a” is nothing other than a function of “b.”  “To be” means nothing other than to be a function and to be a functionary of b.  Similarly, to be a cause of something (causality), the actual effecting of whatever has an effect, that is, the actuality of whatever is actual, is thought “functionally.”  Kant was the first to bring this conception of causality, effecting, to a philosophical concept: “to be caused by something” means: to succeed this “something” in temporal succession in accordance with a definite rule. (HHTI, 41).

The ’world’ of nature is thus understood as a 4-dimensional spatio-temporal world, wherein time (t), added to the three spatial coordinates x,y,z forms the fourth path along which the relational ordering of locations and sequences of movement can extend.

It’s usually considered space-time is like a giant container in which all temporal and spatial positions are accommodated. If this is the case, in what is the container space itself contained in, and when (at what time) is the time container? Or is space nowhere and time not found at any time? If space and time are not objects, what are they? 

Modern metaphysics such as Leibniz (Leibniz, Werke, Vol. 5 Gerh.139) considers unified space-time as measuring/determination of magnitude, and distribution, of the manifold that is given “in” space and time, time being the t in the formula employed in math and physics.  Aristotle determines time as that which counts and is counted in respect of motion (Physics IV xi, 219b1), and Kant sees space/time that which enables a manifold of appearance to be ordered in certain relations (CPR, B34).  Heidegger notes “Space and Time” comprise the framework for our calculative domination and ordering of the “world” as nature and history.  This pervasive measurement of the world in a calculative, discovering and conquering manner is undertaken by modern human beings in a way whose distinctive metaphysical feature is modern machine technology.  This is done to sustain a living space for man and make it further conquerable.    

We thought too the analogical polysemy belonging to the concept of cause with Aristotle and so see “human” / “river” in Holderlin which is not just a particular of a general univocal concept.  While in mathematical space-time any cause/effect in relation is merely a particular of the universal, regarding the relationality of humans/rivers Heidegger says,

When we speak of “human beings” here and throughout these remarks, we always mean the essence of the historical human beings of that history to which we ourselves belong: the essence of Western humankind.  “Human beings” mean neither “human beings in general,” “universal humanity,” nor indeed mere “individual” human beings, nor either some form or other in which several or many human beings are united.   Yet in the concept of the essence of Western humankind we also necessarily, and therefore always, think those essential relations within which this humankind stands: relation to world, the relation to earth, the relation to the gods and to alternative gods and false gods.  These relations are not, however, simply added on to “human beings” in addition to “their” being human; rather to be a human is in itself to be the unity of this configuration … And it is to this alone the essence of the river relates (Heidegger, HHTI, 43)

We do not have with Hölderlin something general here in the relations, or an individual particular instance of something general, but a “singular” relationality with a proper name: “The Ister.” It is thereby questionable whether mathematical spatial/temporal relations are “objective” or if they point to a more original relationality of the human and her dwelling. Recall, the human for Hölderlin is not a substance that is later in relations, but “is” as its relations.