All Protestant denominations reject the notion of papal supremacy over the Church universal and generally deny the Roman Catholic doctrine of transubstantiation, but they disagree among themselves regarding the real presence of Christ in the Eucharist. The various denominations generally emphasize the priesthood of all believers, the doctrine of justification by faith alone (sola fide) rather than by or with good works, and a belief in the Bible alone (rather than with Catholic tradition) as the highest authority in matters of faith and morals (sola scriptura). The "Five solae" summarize the reformers' basic differences in theological beliefs in opposition to the teaching of the Roman Catholic Church of the day.
What is the highest authority in Protestantism for morals?
the Bible