You cast the spell and indicate a single spirit you can sense within range. This may be a creature you can see, hear, or sense using a spell like detect spirits. The spell identifies the spirit's type (and subtypes, if any). If the creature is not a spirit, the spell tells you that as well. The creature gets a saving throw against the spell, if it succeeds, or the spell fails to overcome the creature's spell resistance, you learn nothing.
Focus: A small clay bowl in which you must burn a bit of sage.