Theological Difference between Catholic Church and Protestant Church
The main features of Martin Luthers theology may be summarized in his four doctrines: Sola Scriptura, Sola Fides, Sola Gratia, and Solus Deus.
1. Sola Scriptura
The first doctrine, that of Sola Scriptura (Scripture alone), affirms that the Faith is based only on Holy Scripture and that it is Holy Scripture itself that interprets Holy Scripture. (which means, in effect, that the interpretation is left to the person reading it), while the Catholic Church, in a declaration from the Council of Trent (S.4, 1546), which was taken up again at the First Vatican Council (s.3c.2), teaches that the Faith is based on Divine Revelation (also called Depositum Fidei), and is comprised not only of Holy Scripture (the written part of Depositum Fidei), but also of Tradition (the oral part of Depositum Fidei).
It is not the individual person that has authority over the Depositum Fidei, but the Church. The Church has established which books belong to Holy Scripture, and the Church interprets these books and the data of oral Tradition to define the Dogmas of the Faith. The Ascension is an example of a dogma defined by the Church on the basis of Holy Scripture; the Assumption is an example of a dogma defined by the Church on the basis of oral Tradition.
2. Sola Fides
The second doctrine, Sola Fides (Faith alone) affirms that in order to be saved Faith alone is necessary, and not Faith and works as the Church teaches. In this connection, the sacred Council of Trent (s.6 c.10) cites the following words from the Epistle of St. James, 2,24 Do you see that by works a man is justified; and not by faith only?
Therefore, both Faith and Charity (or works of Charity) are necessary for salvation, and while the false ecumenists act as if Charity alone were necessary, Martin Luther claims that only Faith is. Luthers response to the Epistle of St. James, which clearly expresses Catholic Doctrine, was that of cancelling it from his new canon of Holy Scripture defining it simply as a an epistle of straw. From this we can see how Luther was less motivated by the Holy Scripture than by his own subjectivist presuppositions. The same goes for other parts of the Bible that were cancelled by him.
Moreover, it is necessary to keep in mind that Luther understands Faith in a very different way from Catholics. According to Luther, Faith consists in trusting that God in His mercy will forgive man on account of Christ, while the Church teaches that the Faith consists in accepting Revelation on the authority of God Who reveals it.
Luther anyway had already completely lost the Catholic Faith from the moment that he denied a single article of Faith, because he who denies even one article of Faith, denies the authority of God Who has revealed it.
3. Sola Gratia
In the third doctrine, Sola Gratia, ( Grace alone), Luther affirms that through Original Sin human nature was totally corrupted, so that man became incapable of knowing religious truth and of acting freely and morally, with the result that Grace could not heal man, but only cover his sinfulness. Whereas the Church teaches that human nature is only fallen and wounded, and can be healed with Grace; man can know the truth and possesses free will by means of which he collaborates with Grace in order to act morally, even if this often requires a great struggle.
4. Solus Deus
The fourth doctrine, Solus Deus, (God alone), means that salvation comes directly from God and not through the Church, the Priesthood, the Sacraments, the intercession of the Most Blessed Virgin Mary and the Saints. Luther claims that there is direct access to God. He does not recognize the intimate union between God and the Church: God in His Divinity and God in the Person of Our Lord Jesus Christ+.
a.God, in actual fact, in virtue of His divine and sublime Majesty, has established a hierarchical order in all things, whether they be natural or supernatural, whether they be in Heaven, Purgatory or Hell; and He operates through this intermediary hierarchical order for His own ineffable purposes.
As for the Redemption, He has acted through the Fiat of the Most Blessed Virgin Mary, by means of the Incarnation, the Passion and Death of His Divine Son, and, with regard to the particular point under discussion, by means of the Holy Catholic Church and Her Sacraments.
b. Moreover, God, in the Person of Our Lord Jesus Christ+ has prolonged His earthly life and works in His Church: His life on earth through the Church which is His Mystical Body, and in His works through the Sacraments where He acts in Propria Persona. The most sublime and glorious example of His work is undoubtedly the Holy Mass where He continues to offer and immolate Himself to the Father at every moment of the day and night, and will do so until the end of time.
In fact Luther professes only two Sacraments: Baptism, and that which he was pleased to define as the Supper in substitution for the Holy Mass, the sacrificial nature of which he denied.
II The heretical nature of Luthers theology
So here we have a brief synthesis of Martin Luthers doctrine contained in the forty-one Articles condemned by Pope Leo X with the Damnatio in globo in the Bull Exsurge Domine 1520, ...as heretical, false, scandalous, or offensive to pious ears, as seductive of simple minds, originating with false exponents of the faith who in their proud curiosity yearn for the worlds glory, and contrary to the Apostles teaching, wish to be wiser than they should be.
Now, according to the Code of Canon Law (CIC 1983 Can.751) heresy is the obstinate denial, after having received Baptism, of any truth to be believed by Divine and Catholic faith, or obstinate doubt regarding it Having denied the truth of the Faith, Martin Luther is heretical, that is a formal heretic. Indeed, in virtue of the quantity of heresies that he conceived and taught, the number of protestant sects that he generated, and the consequent damage he wrought for the Catholic Church, he merits the name of heresiarch, or prince of the heresiarchs, or the heresiarch par excellence.