Here is Waton:
The idea of the human person was crystalized in the mind of Christ and instantiated in his life. Once he had instantiated this idea, an infinite number of persons were able to come into existence.
An idea is the essence of reality. What is essence? Essence is that without which a reality cannot exist. When the essence is given, the reality will exist; when the essence is taken away, the reality ceases to exist. Let us consider the electric lamp. It consists of a material body and electricity. The material body and the electricity must cooperate in a definite way that they may constitute an electric lamp. The material body alone or the electricity alone could not be an electric lamp. It would therefore seem that the material body and the electricity are both the essence of the electric lamp. Yet we shall presently see that they are not the essence of the electric lamp. The material body is part of the eternal and infinite matter in the universe; likewise, the electricity is part of the eternal and infinite energy in the universe. The matter and the electricity existed eternally and infinitely, and yet there was no electric lamp. Why? Because the essence of the electric lamp was not in existence. What, then, is the essence of the electric lamp? It is an idea. This idea was crystallized by Edison. Once Edison crystallized the idea of the electric lamp, an infinite number of electric lamps came into existence. So long as this idea will live in the mind of men, so long there will be infinite electric lamps. When this idea will cease to live in the mind of men, then there will no longer be electric lamps. Thus we see that the essence of the electric lamp is neither the material body nor the electricity, but it is the idea.
The idea of the human person was crystalized in the mind of Christ and instantiated in his life. Once he had instantiated this idea, an infinite number of persons were able to come into existence.