What on earth does "consubstantial" mean? It turns out there's a good reason the Church wants Catholics to learn this word. Dominican Father Romanus Cessario, senior editor for Magnificat, unpacks its meaning in the Boston Pilot:
For the last 40 years or so, Catholics have become accustomed to express their belief in the sameness of the Father and the Son by the expression, "one in Being with the Father." This translation came about because certain experts had opined that a literal translation of the Latin term "consubstanialem," that is, consubstanital, would be too unfamiliar to the everyday churchgoer.
However, the expression "one in Being with the Father" does not translate "consubstantialem." The expression is too vague. Since God creates and sustains all that exists, everything in some sense can be said to be one in being with God. Not that everything is the divine nature but that everything outside of God remains dependent on the divine nature for its borrowed existence. The sameness that the Eternal Son enjoys with the Father is not like that. Instead, this sameness arises from the specific substance or nature of the Godhead. Catholic faith holds that each of the three Divine Persons share one and the same divine nature or substance. Just as the mystery of the Blessed Trinity stands at the heart of our belief, so also it grounds our salvation.
The Greek expression adopted at the Council of Nicaea is "homoousious," which is translated into English as "con-substantial." The Eternal Son, who was born of the Virgin Mary, is neither "like" the Father nor "practically the same substance" as the Father. The Eternal Son enjoys the very same substance as the Father. The Son possesses fully the Godhead of the Father. So today, the Church again confesses in the English rendition of the Creed that Jesus Christ is "consubstantial with the Father."
Click HERE to read Father Cessario's entire column.