In other words, to fit, arrange, strengthen. To be complete. To make one what he ought to be. If there is a flaw or an error, the problem is fixed, to conform to the image of Christ. Not just a head knowledge, but spiritual understanding and judgment.
Nobody can agree on everything.
If everybody believes the same things, then God might as well have made us all robots and programmed us like computers. That of the heart. This is something ONLY for Christians. Eye has not seen, nor ear heard, nor have entered into the heart of man the things which God has prepared for those who love Him. But God has revealed them to us through His Spirit.