What did the Council of Nicaea clarify?

 

What did the Council of Nicaea clarify?
Pope Leo issued the Apostolic Letter 'In Unitate Fidei' on the 1700th Anniversary of the Council of Nicaea, with the hope of "encouraging the whole Church to renew her enthusiasm for the profession of faith." 

For centuries," he said, "this enduring confession of faith has been the common heritage of Christians, and it deserves to be professed and understood in ever new and relevant ways. " After all, what unites us is greater than what divides us. 
But what is the faith of the Church on the Trinity?

God the Father is unbegotten, that is, He does not proceed from any other Person.

God the Son—who, as the incarnate Word, is Jesus Christ—begotten, proceeds from the Father (cf. Jn 8:42).

God the Holy Spirit proceeds from the Father and the Son. We can also say that he proceeds from the Father through the Son (cf. Jn 15:26).

God the Father, in knowing himself, produces a Verbum, a Word, which will be:

- God, like the Father, because God’s being and understanding are the same;
- Eternal, because God knows himself eternally;
- Numerically and specifically co-substantial with the Father. To employ an analogy, the more a man understands himself, the closer his concept of himself is to his real self. God’s intellect is infinite; the divine Word (concept) is perfectly one with the source without any kind of diversity;
- Differing from the Father only because He proceeds from him; and
- One and unique, because God knows all other things in knowing himself.

The Word, aside from being God, is the Son of God, as Revelation teaches. 

God the Father, upon knowing himself, engenders the Son, who is a perfect image of the Father. When He loves himself as the Ultimate Good, He loves the Son, and the Son necessarily loves the Father.

There is a bond between them, an infinite love, which receives the revealed name of the Holy Spirit. Since He exists, He is of the same divine nature as the Father and the Son, because in God there is nothing that is not God himself. Therefore, the Holy Spirit is subsistent Love, infinitely perfect, equal in nature to the Father and the Son, but a distinct Person with respect to either of them.

The Holy Spirit proceeds from the Father and the Son. This is a central point of Catholic dogma, taught by the Church in accordance with the common stance of the Greek and Latin Fathers. Even though the formulas used in the East (a Patre per Filium) and West (ex Patre Filioque) differ, they express the same doctrinal content. We all believe that the Holy Spirit proceeds from the Father and the Son as from one principle." 

The difference in formulas—and, above all, a misinterpretation of their meaning—has been the cause of the separation of some Eastern churches from the See of Rome, resulting in a serious rift within the Church.

The separation appeared at the end of the ninth century, when Photius was Patriarch of Constantinople, and reached its consummation by the end of the eleventh century, in the so-called Eastern Schism. The rift continues up to the present day, despite substantial attempts to bridge it.
Nov 30(bis) Sun