Why can't you build a doctrine on one verse here and one verse there?
Scripture is not a private interpretation, so isolating one verse here and one verse there allows any doctrine to be constructed. The proper method compares Scripture with Scripture across Genesis through Revelation, ensuring all parts fit; seeming contradictions fade under consistent study.
Les explains that Peter says in his little epistle that no Scripture is a private interpretation. That means you cannot build a doctrine on one verse of Scripture here and one verse there, because when you do that you can build anything. Instead, it is our prerogative to use all the Scripture from Genesis through Revelation and see that it all fits. Seemingly contradictions may arise, but when you study, they just sort of fade away; they are not contradictory at all.
More Questions
Why can't you build a Bible doctrine from isolated verses?
Because no Scripture is a private interpretation, you cannot build a doctrine on one isolated verse here and another verse there; if you do, you can build anything you want.