Canon Doubt and Uncertainty (CDaU) is the term used for those parts of the In Nomine background that will never be officially defined by Steve Jackson Games and are left up to individual GMs to decide for their own campaigns. Such items have typically included:
- The nature of God.
- The exact extent of Lucifer's power.
- The nature of Jesus.
- The nature of any other major religious figure, such as Muhammad or Buddha.
- The existence/non-existence of free will.
- Whether celestials are truly unique from ethereals or simply a superpowered version of them.
Some of these matters are given more discussion -- but still no defined answers -- in the Game Master's Guide.
On the other hand, some things are mysteries without being CDaU; that is, Steve Jackson Games may choose to give an answer at some point in the future. Examples include the exact status of the Grigori, and what exactly Eli is up to, anyway. (Several options for the latter are discussed, naturally, in Superiors: Eli, by Steve Jackson Games.)