The Bible is the only norm of doctrine and life — the only true standard
      by which teachings and doctrines are to be judged.

Another of Luther's principles was that Scriptures and worship need to be in the language of the people.

Many Lutherans still consider themselves as a reforming movement within the Church catholic, rather than a separatist movement, and Lutherans have engaged in ecumenical dialogue with other church bodies for decades.  In fact, the Evangelical Lutheran Church in America has entered into cooperative "full communion" agreements with several other Protestant denominations.

Luther's Small Catechism, which contains teachings on the Ten Commandments, the Apostles' Creed, the Lord's Prayer, Holy Baptism, Confession and Absolution, Holy Communion and Morning and Evening Prayers, is still used to introduce people to the Lutheran faith, as is the Augsburg Confession.