Since the authority of the Church was denied, some other authority had to be accepted. The parallel authority of Holy Scripture was put forward. Then came the obvious difficulty, that, since there was no external authoritative Church, there was no one to tell you what Holy Scripture meant, and you were thrown back on the interpretation which each individual might make of any passage in the Bible, or its general sense. For instance (to take the leading example) the individual had to decide for himself what was meant by the words of Consecration. But the modern extension of the thing has gone far beyond such comparatively orthodox limits as trusting to the authority of Holy Scripture, even under private interpretation. It has taken the form of basing religion upon individual feelings. Men and women say: "This is true, because it is true to me. I have felt this, and therefore I know it to be true."
Come to think of it, if you want a religion that's really big on sola scriptura today, you probably want Islam. Where the Koran (but only in Arabic!) is the equivalent of Christ to Christians. Or so wrote Newsweek's religion editor, when he explained why last year's riots over allegedly flushed Korans (which turned out not to have been flushed) were perfectly reasonable, because the Koran is so much more important to Muslims than the Bible is to Christians.
Which shows how things can go fatally wrong when people start thinking a book, not God, deserves the honor due to God alone.