Religion’, says St Thomas, ‘denotes properly a relation to God’ and ‘consists essentially in those acts by which man worships God by subjecting himself to his lordship’. (Summa, II-II, 81, 1). Whenever there is a special kind of lordship, there must be a special kind of service, and it is evident that lordship belongs to God in a special and singular way, because he made all things and has supreme dominion over all. Therefore a special kind of service is due to him, called ‘religion’, ‘piety’, or ‘worship’ (Ibid. ad 3. Cf. In Boeth: 8, 2).

But this worship must be of a fitting nature both as regards its object and as regards the one by whom it is offered. Its object, God, is a spirit, and therefore his worship must consist essentially in acts whereby the mind or soul is directed to him. But the worshipper is man composed of body and soul; wherefore his acts of worship must include a bodily element, both to give God the service of the whole man, and to incite himself to internal acts of religion by external ones—‘from things seen to the love of things unseen’.