Here are some great words by Charles Hodge on imputation and justification.
The righteousness of Christ is imputed to the believer for his justification. The word impute is familiar and unambiguous. To impute is to ascribe to, to reckon to, to lay to one’s charge. When we say we impute a good or bad motive to a man, or that a good or evil action is imputed to him, no one misunderstands our meaning. Philemon had no doubt what Paul meant when he told him to impute to him the debt of Onesimus. “Let not the king impute anything unto his servant.” (1 Sam. 22:16.) “Let not my lord impute iniquity unto me.” (2 Sam. 19:19.) “Neither shall it be imputed unto him that offereth it.” (Lev. 7:18.) “Blood shall be imputed unto that man; he hath shed blood.” (Lev. 17:4.) “Blessed is the man unto whom the LORD imputeth not iniquity.” (Ps. 32:2.) “Unto whom God imputeth righteousness without works.” (Romans 4:6.) God is “in Christ not imputing their trespasses unto them.” (2 Cor. 5:19.)
…We use the word impute in its simple admitted sense, when we say that the righteousness of Christ is imputed to the believer for his justification.
…It seems unnecessary to remark that this does not, and cannot mean that the righteousness of Christ is infused into the believer, or in any way so imparted to him as to change, or constitute his moral character. Imputation never changes the inward, subjective state of the person to whom the imputation is made. When sin is imputed to a man he is not made sinful; when the zeal of Phinehas was imputed to him, he was not made zealous. When you impute theft to a man, you do not make him a thief. When you impute goodness to a man, you do not make him good. So when righteousness is imputed to the believer, he does not thereby become subjectively righteous. If the righteousness be adequate, and if the imputation be made on adequate grounds and by competent authority, the person to whom the imputation is made has the right to be treated as righteous. And, therefore, in the forensic, although not in the moral or subjective sense, the imputation of the righteousness of Christ does make the sinner righteous. That is, it gives him a right to the full pardon of all his sins and a claim in justice to eternal life.
rev shane lems
covenant presbyterian church (OPC)