In 1255, in his commentary on the fourth book of Peter Lombard's Sentences, Thomas Aquinas rejected a solution to the problem of sacramental causality, one that was enjoying a certain degree of popularity in the mid-thirteenth century. The opinion that Thomas rejected was that the sacraments effect grace not through an inherent, created virtue but rather through a pact, covenant, or ordination of God that guarantees grace to the person who receives the sacraments, if the latter are properly administered and the recipient places no obstacle in the way of their effectiveness. This type of sacramental causality, termed causality sine qua non, was usually illustrated, Thomas informs us, with the following example. A king might decree that any person possessing a certain leaden coin would receive 100 pounds. In such a case, it would not be the leaden coin that causes the reception of the 100 pounds, but rather the arbitrary acceptation of the token by the king. For Thomas, the leaden coin would be only the occasion for the reward, not its cause. Therefore Thomas rejected this solution which, it seemed to him, would make the sacraments nothing more than the occasion or accidental cause of grace. He sealed his rejection by equating such causality with the way in which the racial color of the builder of a house could be said to be the cause of the house. Thomas maintained this position throughout his life, and, although he altered his solution to the problem of sacramental causality, he in no way altered his rejection of the type of causality based on the example of the king and the leaden coin.