By the doctrine of "diriment impediments" the Pope or a duly constituted representative can declare that a marriage has been null and void from the very beginning because of some impediment defined in the canon law. Canon IV of the twenty-fourth session of the Council of Trent anathematises anyone who shall say that the Church cannot constitute impediments dissolving marriage, or that she has erred in constituting them. The impediments which can annul marriage are described in the official Catholic Encyclopedia, vol. vii, pages 697-698. Among them are impuberty and impotency. Then there is "disparity of worship," which renders void the marriage of a Christian--that is, a Roman Catholic, with an infidel,--that is, one who is unbaptised. Marriage of a Roman Catholic with a baptised non-Catholic constitutes a "relative" impediment and needs a special dispensation and provisoes, such as a guarantee to bring up the children in the Roman faith to give it validity. Another impediment is based on the presumption of want of consent, "the nullity being caused by a defect of consent." "This defect," says the Catholic Encyclopedia, "may arise from the intellect or the will; hence we have two classes. Arising from the intellect we have: insanity; and total ignorance, even if in confuso of what marriage is (this ignorance, however, is not presumed to exist after the age of puberty has been reached); and lastly error, where the consent is not given to what was not intended. Arising from the will, a defect of consent may be caused through deceit or dissimulation, when one expresses exteriorly a consent that does not really exist; or from constraint imposed by an unjust external force, which causes the consent not to be free." Consanguinity and affinity are diriment impediments. Consanguinity "prohibits all marriages in the direct ascending or descending line in infinitum, and in the collateral line to the fourth degree or fourth generation." Affinity "establishes a bond of relationship between each of the married parties and the blood relations of the other, and forbids marriage between them to the fourth degree. Such is the case when the marriage springs from conjugal relations; but as canon law considers affinity to spring also from illicit intercourse, there is an illicit affinity which annuls marriage to the second degree only." Then there is "spiritual relationship"; for example, the marriage of one who stood as sponsor in confirmation with a parent of the child is null and void.