“All Scripture [is] God-breathed and profitable for doctrine, for reproof, for correction, for instruction in righteousness, so that the man of God may be perfected, being fully furnished for every good work” (2 Timothy 3:16-17).
Some historical information from William Burt Pope on Theopneustos :
“The Alexandrian doctors, generally sound, here and there allude to an inspiration common to the prophecies of heathenism and Scriptural prophecies. Tertullian sometimes spoke, as others have spoken since, of an inspiration of all edifying books. Origen and Augustine seem to have admitted that some portions of the Bible were given without inspiration, or by inspiration of a limited degree, some authors, even more than they, laid stress upon the subjective or human element. And this was carried in the Antiochene school, represented by Theodore of Mopsuestia, to an extreme: the writers were mirrors reflecting according to their polish. Theodore was condemned by the Fifth Ecumenical Council for surrendering certain books of the Old Testament and of the New. But, like Luther, who followed him in this, he held a high doctrine as to the inspiration of what he accepted; though, like Luther, applying a subjective canon of his own to determine what ought to be Scripture or what ought to be excluded” (William Burt Pope, A Compendium of Christian Theology; underlining mine).
One might wonder precisely HOW these men Pope mentions defined the word “inspiration” (i.e., Theopneustos or God-breathed)?
Regarding Pope’s statement that Theodore and Luther’s “high doctrine as to the inspiration of what he accepted” — Scripture of course NOT being the absolute criterion as 2 Timothy 3:16 says, but their own subjective and sottish sense.
 James R. White comments (not a blanket-endorsement of White, nor of Warfield), quoting from B.B. Warfield:
“With reference to the meaning of θεόπνευστος, Warfield, having written an extensive treatise on the subject, concluded,
‘From all points of approach alike we appear to be conducted to the conclusion that it [θεόπνευστος] is primarily expressive of the origination of Scripture, not of its nature and much less of its effects. What is θεόπνευστος is ‘God-breathed,’ produced by the creative breath of the Almighty. And Scripture is called θεόπv eυστος in order to designate it as ‘God-breathed,’ the product of Divine spiration, the creation of that Spirit who is in all spheres of the Divine activity the executive of the Godhead. The traditional translation of the word by the Latin inspiratus a Deo is no doubt also discredited, if we are to take it at the foot of the letter. It does not express a breathing into the Scriptures by God. But the ordinary conception attached to it, whether among the Fathers or the Dogmaticians, is in general vindicated. What it affirms is that the Scriptures owe their origin to an activity of God the Holy Ghost and are in the highest and truest sense His creation. It is on this foundation of Divine origin that all the high attributes of Scripture are built’ ” (James R. White, Answers to Catholic Claims: A Discussion of Biblical Authority).
 B. B. Warfield, The Inspiration and Authority of the Bible (Philipsburg, New Jersey: Presbyterian and Reformed Publishing Company, 1948), p. 296.