What has been said up to this point indicates not only the source of the sacraments but also their function and their fruit. Their source is Christ the Lord; their function is to prompt, to instruct, and to humble; their fruit is the healing and salvation of humankind. It is also clear that their efficient cause is their divine institution, that their material cause is their representing by a sensible sign, that their formal cause is gratuitous sanctification, and that their final cause is the medicinal healing of humankind. And because a thing's name comes from its form and its end, these signs are called 'sacraments,' as being remedies that sanctify.
[St. Bonaventure, Breviloquium, Monti, ed. and tr., Franciscan Institute Publications (St. Bonaventure, NY: 2005) p. 214.]