Another purpose of the law is stated in verse 21, as being to bear witness, in conjunction with the prophets, to a future more perfect revelation of God's righteousness. Much of the law was symbolic and prophetic. The ideal it set forth could not always remain unfulfilled. The whole attitude of that system was one of forward-looking expectancy. There is much danger lest, in modern investigations as to the authorship, date, and genesis of the Old Testament revelation, its central characteristic should be lost sight of; namely, its pointing onwards to a more perfect revelation which should supersede it.
He states that twice in this passage (vs. 20 to 24), and it underlies his view of the purpose of law. In verse 20 he asserts that 'by the works of the law shall no flesh be justified,' and in verses 23 and 24 he advances from that negative statement to the positive assertion that all have sinned. The impossibility of justification by the works of the law may be shown from two considerations: one, that, as a matter of fact, no flesh has ever done them all with absolute completeness and purity; and, second, that, even if they had ever been so done, they would not have availed to secure acquittal at a tribunal where motive counts for more than deed. The former is the main point with Paul.
In verse 23 the same fact of universal experience is contemplated as both positive sin and negative falling short of the 'glory' (which here seems to mean, as in John v. 44, xii. 43, approbation from God). 'There is no distinction,' but all varieties of condition, character, attainment, are alike in this, that the fatal taint is upon them all. 'We have, all of us, one human heart.' We are alike in physical necessities, in primal instincts, and, most tragically of all, in the common experience of sinfulness.
Paul does not mean to bring all varieties of character down to one dead level, but he does mean to assert that none is free from the taint. A man need only be honest in self-examination to endorse the statement, so far as he himself is concerned. The Gospel would be better understood if the fact of universal sinfulness were more deeply felt. Its superiority to all schemes for making everybody happy by rearrangements of property, or increase of culture, would be seen through; and the only cure for human misery would be discerned to be what cures universal sinfulness.