In Romans 14.1–15.13, St Paul teaches on ‘the weak’ and ‘the strong’, saying that the strong should accommodate the scruples of the weak, but he also pushes the Christians in Rome, as they live in harmony, to develop a common mind rather than merely agreeing to disagree. This is a pattern he consistently upholds from Romans 12 to Romans 15. In 12.1, he urges the brethren to offer up their bodies (τὰ σώματα ὑμῶν, plural) as a sacrifice that is living, holy, and acceptable to God (θυσίαν ζῶσαν ἁγίαν εὐάρεστον τῷ θεῷ, singular); in 12.2, rather than a transformation of believers’ minds severally, he speaks of a single transformation of the mind (τῇ ἀνακαινώσει τοῦ νοός); in 12.15–16, he says, ‘Rejoice with them that do rejoice, and weep with them that weep; be of the same mind one toward another’; in 15.5–6, ‘Now the God of patience and consolation grant you to be likeminded one toward another according to Christ Jesus: that ye may with one mind and one mouth glorify God, even the Father of our Lord Jesus Christ.’ Respect for differences in conviction, then, is to serve a higher end: the formation of the mind of the Holy Spirit in the Church, whether through diverse spiritual gifts animated by one Spirit or through a unity even with diverse convictions on food, days, and other such things the Reformed tradition has called adiaphora (things in themselves indifferent).
Those who are strong, then, are not to impose their views on those who are weak, whose faith in God does not depend on (say) dietary and festival laws. No doubt the trajectory in the long term is toward strength, whereby the people will be able to worship God without scrupling about the Mosaic Law, recognizing what things are truly matters indifferent and not matters de fide (of faith). As Ben Witherington notes in Paul’s Letter to the Romans: A Socio-Rhetorical Commentary, 338, St Paul in Romans 14.14 and 14.20 says plainly that no food in unclean in itself. He is certainly not lacking in a strong position. Nevertheless, he says that judging others and criticizing them for their scruples is not the way. It seems to me that respect for variation in convictions and practices is itself part of the common mind that St Paul wants to cultivate in the Church, by the power of the Holy Ghost.
In the use or disuse of Christmas among Reformed Christians, I think strong or weak faith might appear on both sides. A weak Anglican brother may be one who mistakenly thinks that observance of Christmas is essential to his righteousness; a weak Dissenter brother may be one who mistakenly thinks that nonobservance of Christmas, and use of the Lord’s Day only as a day set aside for worship, is essential to his righteousness. A wise strong Reformed Christian may worship with the weaker Anglican brother on Christmas Day, and even through all twelve days of Christmastide all the way to 5 January, but he will also not impose Christmas as an observance upon the weaker Presbyterian brother who believes that the Lord’s Day alone should be observed, nor will he tempt that brother to act against conscience. In the pulpit, he may preach on the Incarnation of our Lord; at home, he may invite both brethren to dinner in Christmastide, that they may rejoice together in the saving truth of our Lord’s coming to us as a man. In the long term, the faith of both weaker brethren will strengthened as they unite in the Lord, both aware of the other’s conviction and, through respect, growing in faith in what is indeed essential to righteousness.
In recommending the use of Fridays as fast days and the use of Lent as a seasonal fast, the Book of Common Prayer also wisely avoids imposing particular practices, whether in choice of meats, forgoing of food, or particular private devotions. This restraint serves the weaker brother who feels that he must not eat land meat, lest he indulge himself in a season of corporate fasting; likewise, it serves the weaker brother who feels that he must not intentionally avoid land meat, lest he fall to popery. What will bring them together is a common focus on the promises of God’s word (15.4–6), through which God will make them likeminded and glorify God with one mind and one mouth. So preaching to an audience with both kinds of weaker brethren may focus on what God promises to those who repent of their sins and fast to seek his face, who mourn that they may be comforted.
One place in which I am uncertain is the fulfilment of the day of rest. I agree with Douglas Moo, in Encountering the Book of Romans, when he says of the commandment in the Mosaic Law, ‘As Hebrews suggests, the Sabbath command has found its fulfillment in Christ, so that all of us who have access to God through faith live in an eternal “Sabbath-rest”.’ The chief way in which we fulfil this law in spirit is to rest in the finished work of Christ, being justified by faith and not by works of the law. Nevertheless, my own conviction is that Lord’s Day rest is necessary not only to help us ourselves rest from our labours and trust in the Lord, but to give others the opportunity to do so as well. This is a secondary moral application of the Fourth Commandment, important against the claims of the idols of our day, not least the idol of global neoliberal capitalism. I think the practice of a weekly day of rest, which cannot be fulfilled unless practised by the body of Christians and not merely by individuals, is undermined by the buying and selling that Christians do on Sunday, which creates incentives contrary to those I think we should be committed to. Sometimes Christians buy and sell on Sundays to facilitate their own practices at church, such as catered church lunch after the Sunday morning service. Suppose that one is dating a girl who does not scruple at buying groceries on a Sunday, and she fears that avoiding Sunday shopping out of respect for her husband’s convictions would be an undue burden on her; perhaps she thinks the solution is to agree to disagree, not interfering with each other’s individual practices. I think this is not what St Paul meant, but such a situation seems a difficult knot for a family to untie.