OK, let me make some enemies. This is not a subject for amature conjecture. I am trained as an Historic-Redactive Analist. We are the nit-pickers who put the Holy Writ under the microscope and through the computer to disassemble such things as syntax, gramatical consistency, stilistic “fingerprints” etc., and place it in it’s historic setting. This to better understand exactly what the writer was talking about and bust the baloons of the uneducated “jump on a stump” preachers who consistantly draw wild conclusions, such as Mellenialism. That does not mean that we doubt the validity of the revealed truth, we just insist upon complete and absolute fidelity to what was actually written, or re-written as many books of the Old Testament started out as one thing, only to be recast at a later date to another purpose. We are the ones charged with finding out what God was saying both originally and in the latter itterations, and you would be surprised to find out how frequently, and by how many different people what we have now was rewritten before we got it, which is after all the very nature of prophecy. I assure you that Mark, not Mathew is the earliest book, though it is later than the Epistles, and that Q does exist, sort of. What Q is, is nether specified nor important. The term “Q” comes from the German word for “unknown” and it probably never was a book as such. It is unknowh, because there is no “copy” of it that we can study directly. It is the common source for Matthew and Luke, who also drew upon Mark, was probably an early body of teaching of that extended community of the Church the first three Gospels were written in, and was most likely oral. Mat and Luke would not have thought of it as a formal “thing.” It was simply the teaching that all knew. It’s fingerprints are all over Matthew and Luke, as they copied complete “paragraphs,” arranging them to tell the Good News in the manor and order most digestable to their particular flocks. Along with Mark and Q, Matthew had a source called "M,’ and Luke had a source called “L”. “Q,” “M,” and “L” are academic constructs, which should be of no interest to the layity. They are technical devices which are not transparent to those who are not specifically trained in them, and frankly that includes most seminary graduates. Do you have to be an expert on Magnetic Resonence Imaging to go for an MRI when your doctor tells you to, or do you trust him to tell you why your hip hurts and that all your worldly goods are about to end up property of the medical industry? Leave the heavy lifting to the experts who serve and answer to the Magesterium. You will note that I have said nothing about John. John comes from outside the extended community of Matthew, Mark, and Luke, and is thought to have had only one source, not shared with the other three. This is my professional oppinion as an academic, and is accepted by the pearage. As to what I personally believe, I believe what the Church in it’s magesterial capacity teaches.