The co-equality of the Father and the Son is in my opinion a philosophical trick of the Constantinople council of Trinitarian theologians.
Firstly, here is a philosophical trick to allow me to assert that 1 equals 2. 1 is an integer. 2 is an integer. 1 is an integer in the same sense that 2 is an integer, so they are equally integers. Co-equal as integers. 1 and 2 are therefore equally integers. So in this sense they are equal. Obviously is does not mean that 1 equals 2. It is just clever philosophy. The Trinity tries the same philosophy. It says the Father is something in the same sense that the Son is that same something, and the Father is that something equally to how the Son is that same something. The same something it calls homoousios. This allows it to say that the Son is co-equal to the Father. They are co-equally homoousios. But this homoousios is invented. How does it work with something more concrete and real? Let us try the Gospel, which they each teach. The Father is a teacher of the Gospel. The Son is a teacher of the Gospel. Is the Father a teacher of the Gospel in the same sense that the Son is teacher of the Gospel. Are they equally teachers of the Gospel? Are they co-equal as teachers of the Gospel? No. The Father is not a teacher of the Gospel in exactly the same sense as the Son. The Son is not the source of what is taught, whereas the Father is the source, so they are not equally teachers of the Gospel. Almost but not quite equal in this sense. So it does not mean that the Father equals the Son. Not in that sense. And of course the Father is greater than the Son, just as 2 is greater than 1. So in neither sense is the Son equal to the Father. The idea of their co-equality is a philosophical trick.
