When we say that something is static, we mean that it does not change. When we say that something is a field, we mean it as a group of objects that have something in common with each other. When we say that a property is external, we mean that it only appears in relations to that which is outside of the object.
Putting all of these together, Ti is the attribute of fields that is unchanging in its relationship to other fields. If you were to put a group of fields side by side, then Ti is that part of them that is not changing, but is staying constant. And yet, there is a relationship: the fields are sharing something between themselves by means of this stasis.
This something is so fundamental to our experience that we often consider it without really thinking about it, because it is in substance thought itself. It is structure, the very fact that the fields are persistently interconnnected. That they are interconnected means that they share a common attribute between them, an attribute shared also by all of their objects. (or else the object set would not be a field.) This attribute relates their defining characteristics and creates effect. Thus we say, upon observation, that the attribute of the fields' relation combines their respective properties into one synthesized property, thus establishing "cause" and "effect".