Quoted from TheLaw:
Whole point of an ambiguous ending is that no one knows, not even the people that made it. Even if they say they they do, it doesn't matter; like Blade Runner.
That's what I think adds to the cult classic status; the fans watching multiple times creating & debating random theories.
Quoted from Pinstym:
I believed the kerosene theory till I saw this. Spoilers if you haven't seen John Carpenter's The Thing.
Watch "John Carpenter''s THE THING - "Molotov whisky" theory examined" on YouTube
I watched that one too. He makes a few good points but ultimately the chance of Mac finding a bottle of regular whiskey or having a Molotov Whisky are equal in likeness for me. Maybe he goes back to his shack and grabs a bottle but why then would he stumble back out into the cold? Why not just stay in your shack?
The Thing is a great movie because of the special effects & the suspense. Who is the thing at any given moment in the movie? Who really knows? Can you tell from the clothes(theory) or is it the eyes(theory)? Testing their blood is the only way to be sure.