Chapter — Gury-Ballerini, Compendium of Moral Theology (8th ed., 1884)
Chapter III. On the Modifications of Contracts
¶1.
By the name of modifications are designated certain clauses added beyond the nature and essence of contracts, so that now they strengthen the obligation of the same contracts, now also they increase or determine it, now they suspend or destroy it.
¶2.
But the principal modifications of contracts are: 1. oath; 2. modes; 3. conditions. - These three must be treated briefly.