Originally Posted by bpress54
Well, you wouldn't say "he set his bag on the ground" if he was inside, just like you wouldn't say "the ship sank to the sea ground." It's all about context.
Correct about context. Forests and caves have floors. Otherwise outside your typically setting something on the ground, in the dirt, on terra firma, etc.
If you are inside and set something in the dirt, it is probably a commentary on housekeeping.