In tonight's game, the knight went down to 0 hp. Later that round, the paladin granted the knight 7 temporary hp. As the DM, too lazy to slow the game down to look the precise rules up, I ruled that the knight returned to consciousness and was no longer dying. Was I right? How do temporary hp interact with the unconscious and dying states?
That's a good question. (And I agree with your off-the cuff ruling, as any decision made quickly is better than one that disrupts the flow of the game.)
Let's start with some definitions:
Thus, because temporary hit points do not count as "healing" the character who was dying would remain at 0 hit points, unconscious, and should continue to make death saving throws. However the temporary hit points would protect against subsequent Coup De Graces and other DM agression.