Sola Scriptura from the earliest days of the Christian faith.

Proclaiming Sola Scriptura is not an uncommon thing for us to say, that is the total trust that the sufficiency of Scripture as our supreme authority in all spiritual matters. Most evangelicals would affirm this without any problem but some will not without further discussion in clarification of what the term means, and that is ok. It is good to define what is meant by the term and how it applies to us today. However, there are some groups, Roman Catholic, Eastern Orthodox, Coptics, etc., who do not hold to this and would claim that it is a late invention of the “rebellious” reformation movement. Is Sola Scriptura a new idea, new being relative to the overall length of the existence of the Christian church?
Looking back at church history is an excellent way to see how our predecessors dealt with issues, how they tried to define and explain scripture and scriptural principles to those around them. I happen to love reading church history with special attention given to the era that ranged from A.D. 200 to around A.D 400-500 or what is commonly recognized as the Patristic era. There are a great number of things that can be learned from and myths to be discarded about the Patristic era. The issue of the supremacy of scripture or a nascent form of Sola Scriptura is evident among the Patristic writers as the rule of faith, and it was often directly referred to as an essential aspect of proper faith.
Clement of Alexandria who lived from around 150 to 215 had some remarkable things to say during his life of faith and ministry. Particularly important is his statement on how scripture is the basis for our knowledge. He focused on the Word of God being revealed and proclaimed in scripture. He had the following to say about scripture;
"The Lord is the source of our teaching – we have him by the prophets, the Gospel and the blessed apostles, speaking “in different ways and at many times.”
Here, of course, he paraphrases Hebrews 1:1 as he emphasizes that the message we have is of divine origin, it comes from God to us by way of his chosen messengers.
He then goes on to the real emphasis of faith;
"Whoever believes the scriptures and the voice of the Lord is being faithful. The Bible is the criterion of our knowledge. What is subjected to scrutiny is not believed until it is subjected to this test, so that whatever needs to be examined in this way cannot be regarded as our first principle."
Clement emphasizes the essential nature of scripture in our ability to have true faith. He declares without hesitation that it is the scripture alone by which we have the criterion of what we know. Criterion means a principle or standard by which something may be judged or decided. He establishes scripture as the first principle of our faith and from that comes everything that we are to believe under the scrutiny of scripture.
Consequently Clement continues this line of thought,
"Therefore, as is only reasonable, we grasp the undemonstrable first principle by faith, and then we receive abundant proof of the truth of the first principle from the first principle itself. In this way, we are trained up by the voice of the Lord to a knowledge of the truth."
Without saying it the way we might today, Clement of Alexandria is telling us that it is by scripture that we can hear the voice of the Lord, and that scripture is the first principle of our faith while affirming that scripture interprets scripture.
Sola Scriptura from Clement of Alexandria, an early church leader writing in the very early 3rd century paved the way for how we should think about scripture and how to engage in hermeneutics.