The principle that, once married, the parties are bound no longer by their agreement but by the nature of marriage, belongs to civil law too. When formed this relation is no more a contract than 'fatherhood' or 'sonship' is a contract. As a practical matter resulting from its being God-made, marriage is not indissoluble just because the parties at their wedding made vows of lifelong fidelity. It is indissoluble because it is marriage. The difference between divorce and nullity is therefore about as wide as it is possible to conceive.
Divorce claims to break up a marriage actually in being.
The incidentals may roughly be lumped together as the form or ceremony. In all the more important contracts the authority having jurisdiction insists on some special form. The absence of an essential must be fatal. If a contract is declared null by any court on the ground that one of the essentials was lacking, there is no point in urging that all the incidentals were in order. In this preliminary discussion it may seem slightly pedantic to point out that an agreement to do one thing does not make a contract to do something different.