The Five Solas

The Five Solas summarize the core doctrines that were established during of the Protestant Reformation in the 16th century.

Sola scriptura (Scripture alone).
The Bible is the only authoritative Word of God, and is the only infallible voice of the Christian church. Alternatively, while Catholics affirm infallibility of the Bible, they also believe in the infallibility of the Pope and the Ecumenical Councils. Drawing from history, consider the Galileo affair in the 17th century. Today, grade school history books generally neither teach that Galileo respected the Bible, nor that the Catholic church got their ideas of geocentricism (idea that the earth is at the center of the Solar System, around which everything revolves) from the modern scientists of the day, who were merely drawing upon previous ideas originating from Aristotle. It was by pressure, from the modern scientists that did not want to lose their standing in the scientific community, that the Catholic church caved and demanded Galileo to rescind his position of heliocentricism (idea that the sun is at the center of the Solar System around which the earth revolves). The bottom line was that, Galileo was not blamed for criticizing the Bible but for disobeying papal orders. Hence, the lesson to be learned is that the only authority for ultimate truth is God's Word. We should lean not on our own understanding (Proverbs 3:5), but by every word that proceeds from the mouth of God (Matthew 4:4).

Solus Christus (Christ alone).
This represents the exclusivity of Christ. That is Jesus Christ is "the way, the truth, and the life (John 14:6), and there is no other name by which men can be saved (Acts 4:5-12). Salvation neither comes by Mary, the saints, false gods, nor the sinner himself.

Sola gratia (Grace alone).
Salvation is granted only by way of God's sovereign grace, not through any works or merit by the sinner (Ephesians 2:8-9). Eternal salvation is a gift that is not earned; it is granted. Throughout the scriptures and especially Paul's epistles, grace is presented as a gift bestowed on the elect for His sovereign purpose and glory. Nothing can resist the sovergeign will of God (Daniel 4:35, Psalm 115:3, Romans 9:14-18). Thus, there is no place for self-righteousness in the Christian faith. For more study on this topic of salvation coming by grace alone, refer to the article by R.C. Sproul, The Pelagian Captivity of the Church.

Sola fide (Faith alone).
Salvation comes through faith only, not by works. Faith is the medium through which God's grace is initially revealed. Faith does not come from ourselves, but is itself the result of grace (Ephesians 2:8-9). However, saving faith is authenticated by good works (James 2).

Soli Deo gloria (Glory to God only).
All the glory, praise, and honor goes to God and Him alone for our salvation (Romans 16:25-27). Not to saints, not to popes, not to Mary, etc... Glory to God is due not only for the power and atoning work of salvation, but even the very granting of that saving grace to the believer (John 6:44-45).