When evangelical Christians speak of the Bible as “inspired” they are referring to the unique nature of authorship for all 66 books of the Bible. The key verse referring to this reality is found in Peter’s second Epistle where he describes the production of Holy Scripture as something never “produced by the will of man”, but rather came into written form as “men spoke from God as they were carried along by the Holy Spirit” (2 Peter 1:21) .
This is the phenomenon the Apostle Paul is referring to when he says that “all Scripture is breathed out by God” (2 Timothy 3:16).
This uniqueness is often described as “dual authorship”. In one sense, all Scripture is written by God. It is also true that each biblical book is authored by the human writer ascribed to it. For example, the Apostle Paul wrote his Epistle to the Romans under the inspiration of the Holy Spirit. Wayne Grudem describes the concurrent truths of dual authorship when he says:
God’s providential oversight and direction of the life of each author was such that their personalities, their backgrounds and training, their abilities to evaluate events in the world around them, their access to historical data, their judgment with regard to the accuracy of information, and their individual circumstances when they wrote, were all exactly what God wanted them to be, so that when they actually came to the point of putting pen to paper, the words were fully their own words but also fully the words that God wanted them to write, words that God would claim as his own (Wayne Grudem, Systematic Theology p81).
The Bible stands alone as unique among all literature because it is ultimately and entirely authored by Almighty God and this is what is meant when Christians refer to all Scripture as “inspired”.