To those who argue that as long as you have the right doctrine but no practice you'll still go to heaven, Augustine discusses what it is to truly have Christ. "Whoever, then, has Christ in his heart, so that no earthly or temporal things—not even those that are legitimate and allowed—are preferred to Him, has Christ as a foundation. "
When we love Christ above all else, then we have the sign that we have truly believed the Gospel. When our lives do not match this claim, we have the sign that we are liars:
But if these things be preferred, then even though a man seem to have faith in Christ, yet Christ is not the foundation to that man; and much more if he, in contempt of wholesome precepts, seek forbidden gratifications, is he clearly convicted of putting Christ not first but last, since he has despised Him as his ruler, and has preferred to fulfill his own wicked lusts, in contempt of Christ’s commands and allowances. Accordingly, if any Christian man loves a harlot, and, attaching himself to her, becomes one body, he has not now Christ for a foundation.We are tried by "fire", in that those who stick to the faith and keep their actions pure are those who are shown to have Christ as the sure foundation. Those who pursue sin are shown to be false in their claims to faith. They will not see heaven.