Knowledge and activity are essential parts or features of a greater whole, namely the logical system described here. Therefore they cannot be viewed in isolation. They get their meaning from the whole and from their relationship with each other and with other similarly fundamental terms.

Above all thing and space. These are, in a way, as diametrically facing one another as knowledge and activity. In the extreme, so to speak, space is the opposite of the thing, that what resides between the things, what separates them. But of course each thing occupies some space; and space may be treated as a thing — representing knowledge — arising through activity.

These concepts belong together, for they are four corners of one and the same figure.