This specific relationship cannot be destroyed or replaced by another.

This specific relationship cannot be destroyed or replaced by another. Whenever you consider the quiddity of a thing that has an identical relationship to being and non-being, neither of them being rationally essential for it, that thing is technically designated as "contingent," in the sense that there is nothing within its essence necessitating either being or non-being. If a thing in its own essence requires its own non-being, then its existence is impossible.

Finally, if being emerges from within the essence of a thing in such a way that reason cannot regard it as dependent on anything else, the existence of that thing is designated as necessary. It is an independent being, free of all need and subsisting by means of its own essence; its existence is the source of all other beings, while it is not subject itself to any need or condition.

It should be added that material existence cannot in any way acquire the attribute "necessary," because the existence of any compounded material entity is conditional on the existence of the parts that comprise it; it is dependent on its own parts both for its origin and for its survival. Matter has different aspects and dimensions; it is immersed in quantity and multiplicity; and it acquires its various dimensions by means of attributes and properties.

The necessary being, by contrast, is free of all such properties. ***** All the phenomena that once did not exist and then came into being once possessed abstract notions of being and non-being. When they hastened toward the point of being, this was as a result of a cause that impelled them in that direction. It was an impulsion, an external factor, that drove them in one direction instead of the other.

In other words, the existence of a cause was the agent of being, just as the non-existence or absence of a cause is the agent of non-being. Of course, a phenomenon that comes into being as the result of the existence of a cause never loses its essential neediness; it will always remain a being characterized by need. For this reason, the need of a phenomenon for a cause is permanent and indissoluble; its relationship with the cause will never be severed for an instant.

Were the relationship to be severed, the existence of the phenomenon would immediately yield to non-existence, in just the same way that the very instant an electricity generator stops working, all the bright lamps connected to it fall dark.