To illustrate, consider the relation of parent to child. Hence, the child is related to the parent in a real or constitutive way, which is not the case considered the other way around. This concrescence is thus nothing else than the 'real internal constitution' of the actual occasion in question. To continue the example, the process by which a unique person emerges from its inheritances and experiences is its concrescence. An event cannot take into itself, or prehend, every experience in the same manner.
Some selection is necessary among the available matters of fact.
So the subject, even while it is being constituted by its prehensions, prehends past data either positively or negatively. It makes this selection on the basis of its own subjective aim. The process by which new events emerge, through prehensions that can be either positive or negative, requires a selection. The synthesis of the new event, and hence the creation of novelty, is the result of what prehensions are available and how they are prehended. How a subject prehends a datum is determined by its subjective form.