Index: LOOK UNDER shows nothing unless the player has a light
Description: Visibility set so that looking under objects produces no result unless the player has a light source to shine there (regardless of the light level of the room).
The Schoolhouse is a room. "Though normally comfortable, the room is dark and menacing during the storm; rain sheets on the windows, and you can barely see the flash of the lighthouse only a few miles away."
The cabinet is a fixed in place openable container in the Schoolhouse. The hurricane lantern is a thing in the Schoolhouse. "A hurricane lantern hangs from a peg." The lantern is lit.
Visibility rule when looking under something:
if the player is carrying a lit thing (called lamp):