Why was Martin Luther so against the Book of James?

Answer 1

Because James said in 2:24 "You see that a person is considered righteous by what they do and not by faith alone," which was counter to Luther's theology of justification by grace through faith alone.

Additional Comment:

As many Christians today assume 'salvation and justification' are one and the same - they simply are not, though there are related.

Ephesians 2:8New King James Version (NKJV)

8 For by grace you have been saved through faith, and that not of yourselves; it is the gift of God,

Justification is being 'made just, right or righteous.' Literally it means to be made 'straight' particularly lined up with God and His ways and is integral to salvation.

Paul called this 'imputed righteousness' (see Romans 4:20-25 and James understood this as well (James 1:19-20). Yet James 2:24 was speaking of maintaining ones justification by doing the good works of God's Spirit within us just as Paul understood as well and his disciple Titus' book is about 'good works:

Romans 2:13New King James Version (NKJV)

13 (for not the hearers of the law are just in the sight of God, but the doers of the law will be justified;

Jesus explained that all would recognize His followers by God's love expressed through them (John 13:35) James and his fellow disciples would prove their faith via their works. In modern terminology it is like, talk is cheap so put your money where your mouth is or prove your words with your actions.

Talking about Christianity is one thing. Acting on it is quite another. James lived by his brother's teachings and taught other Church members to do the same. Perhaps if Martin Luther would have fully released himself from his prior teachings and taken the time to pray and study all the Scriptures with this open mind, he would have come to this same conclusion on the value of the Book of James.