Reason versus Justification

Reason thinks as follows: If you have been justified, you cannot be a sinner. But they do not understand the magnitude of divine mercy and the efficacy of faith, that is, they cannot discern true from false. They do not think that God can count us righteous while sin remains. His imputation is greater than our purity; the substance remains. The imputation is greater than all the angels and the whole world. - Martin Luther