Apologists frequently quote the writings of the Church Fathers, Doctors of the Church and other holy saints to defend dogmas, disciplines and the teachings of the Church. The Catechism of the Catholic Church is another often quoted source.
How does one justify the use of these sources, in order to defend the teachings of the Church, to someone who professes belief in Sola Scriptura?
Likewise, we can quote modern day theologians, but how can we be sure that they are orthodox* in their writings and then justify their teaching to Sola Scriptura Protestants?
(*This does not refer to Karl Keating, Jimmy Akin or anyone else at Catholic Answers.)