Even though we have refused to regard experienced space, in the sense of mere experience of space, as something merely psychological, it is on the other hand not an object removed from the subject. As we have stressed from the start, it is a question of the relationship between the human being and his space, and thus also of the structure of human existence itself, insofar as this is determined by his relationship with space. It is in this sense that we speak of the spatiality of human existence. This term does not imply that life — or human existence (Dasein) — is itself something spatially extended, but that it is what it is only with reference to a space, that it needs space in order to develop within it.
It is in this sense that Heidegger in Being and time very clearly worked out the question of the spatiality of human existence, even if he could not develop it more detail in the general context of that work. Just as, according to him, one must distinguish between temporality as a structural form of human existence and time as an objective process, so we must also distinguish between space —whether it is experienced or mathematical space is irrelevant to this question — and spatiality. Spatiality is a definition of the essence of human existence. This is the meaning of Heidegger’s statement: ‘The subject (Dasein), if well understood ontologically, is spatial.’ That it is spatial does not therefore mean that the human being occupies a certain space with his body, in the same way as any other mass, and also occasionally — like the proverbial camel at the eye of a needle —is prevented from slipping through openings that are too narrow. It means that the human being is always and necessarily conditioned in his life by his behaviour in relation to a surrounding space.
This is also what Minkowski has in mind when he stresses: ‘Life spreads out into space without having a geometric extension in the proper sense of the word. We have need of expansion, of perspective, in order to live. Space is as indispensable as time to the development of life.’
At the same time we are still expressing ourselves carelessly if we say that life takes place ‘in space’. Human beings are not present in space as an object, let us say, is present in a box, and they are not related to space as though in the first place there could be anything like a subject without space. Rather, life consists originally in this relationship with space and can therefore not be separated from it even in thought. It is basically the same problematic of ‘being-in’ that Heidegger develops with reference to ‘Being-in-the-world’, when he stresses: ‘Being-in, on the other hand, is a state of Dasein’s Being; it is an existentiale. So one cannot think of it as the Being-present-at-hand of some corporeal Thing (such as a human body) “in” an entity which is present-at-hand … Being-in is thus the formal existential expression for the Being of Dasein, which has Being-in-the-world as its existential structure.’
(BOLLNOW, O. F. Human space. Christine Shuttleworth. London: Hyphen, 2011)