Let's amend the premise by taking "space" out of it:"our acquired knowledge of objects comes to us from having seen them in certain relations to other objects". Space points do not come with labels attached, even when we measure distances they are distances between markings of some sort, not points. And we can easily establish relations between objects without space, say numbers 2 and 17, or even vectors and operators in infinite-dimensional spaces. They are not physical objects of course, and space is around for those, but even physically objects are demarcated by other objects, and their characteristics are contrasted to characteristics of other objects.
Come to think about it there is no space involved in any of it, it is merely kept, and perhaps constructed, as framing. Psychologists established that our visual perception starts with a flat and spotty impression on the retina, which is then filled in and 3-dimensionalized by the brain. Kant even believed that this imposition of flat 3D space is the source of synthetic a priori knowledge which will forever subject our physical theories to 3D Euclidean geometry. As it turned out, even the space of visual perception is slightly hyperbolic.
The idea of empty independent absolute space only came to prominence after Newton, who adopted it because it was the simplest way to express classical mechanics (modern textbooks have to go through a complication of reference frames). Before that relational theory of space was a consensus since Aristotle. Descartes identified space with matter, so that when matter moves the space moves, it does not leave some empty space behind to arrive at a new one. Leibniz gave the most comprehensive expression of the "ideality of space" in relational theory. He held that "(i) a body comes to have the ‘same place’ as another once did, when it comes to stand in the same relations to bodies we ‘suppose’ to be unchanged... (ii) That we can define ‘a place’ to be that which any such two bodies have in common... And finally that (iii) space is all such places taken together. However, he also holds that properties are particular, incapable of being instantiated by more than one individual, even at different times; hence it is impossible for the two bodies to be in literally the same relations to the unchanged bodies. Thus the thing that we take to be the same for the two bodies — the place — is something added by our minds to the situation, and only ideal. As a result, space, which is constructed from these ideal places, is itself ideal: ‘a certain order, wherein the mind conceives the application of relations’".
When working on general relativity Einstein noticed that if we know gravitational field around a region in space there is no unique way to extend it into that region, but that different extensions are physically equivalent despite assigning different field values to different spacetime points. This came to be called the "hole argument". Einstein concluded from it that individual spacetime points as such are physically meaningless and accepted the relational theory:"People before me believed that if all the matter in the universe were removed, only space and time would exist. My theory proves that space and time would disappear along with matter."
