The teaching of the purity of scripture seems to have changed over the years.
The Westminster Confessions hold that only the Hebrew and Greek were “immediately inspired”, which could be taken as a reference to the autographs. They go on to say that the word of God has been “kept pure in all ages”.
The confession is clear about the Greek NT being pure in all ages, yet scholarship throughout the ages is moving further and further from this position. Scholars either re-define purity as something that is “almost” pure, or reject the idea of purity throughout the ages all together and suggest that they are trying to get back to the purity of the originals (as if the text must be reclaimed, and has not been kept pure in all ages).
Modern thought on purity can be seen in The Chicago Statement on biblical Inerrancy. This statement claims that inerrancy applies only to the original manuscripts (autographs), not to the copies (apographs).
Scholars of the past had different ideas, as they seemed to hold the apographs in a higher esteem…
John Owen said,”the purity of the present original copies of the Scripture, or rather copies (apographa) in the original languages, which the Church of God doth now and hath for many ages enjoyed as her treasure.”
Francis Turretin wrote in his Systematic Theology, “By original texts, we do not mean the autographs written by the hand of Moses, of the prophets and of the apostles, which certainly do not now exist. We mean their apographs which are so called because they set forth to us the word of God in the very words of those who wrote under the immediate inspiration of the Holy Spirit.”