Fact is the undifferentiated terminus of sense-awareness; factors are termini of sense-awareness, differentiated as elements of fact; entities are factors in their function as the termini of thought.

The entities thus spoken of are natural entities.
Thought is wider than nature, so that there are entities for thought which are not natural entities.
When we speak of nature as a complex of related entities, the 'complex' is fact as an entity for thought, to whose bare individuality is ascribed the property of embracing in its complexity the natural entities.

It is our business to analyse this conception and in the course of the analysis space and time should appear.

Evidently the relations holding between natural entities are themselves natural entities, namely they are also factors of fact, there for sense-awareness.

Accordingly the structure of the natural complex can never be completed in thought, just as the factors of fact can never be exhausted in sense-awareness.