believed that salvation is achieved through faith alone;

this belief is known as sola fide, which is a central tenet of Protestant Christianity. It teaches that individuals are saved by placing their trust and belief in Jesus Christ as their savior, rather than by their own good works or efforts. This belief is based on passages in the Bible, such as Ephesians 2:8-9, which states that "For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast."