— You can't come up with a formula to change the way you experience the world.
— All I have to do is apply my mind.
— Well, then, at least throw away your opium. It's that that causes the visions. Just... throw it away. While it's there, it's a temptation. How much have you got left?
— Seven tonnes.
— Seven tonnes?
— Yeah. I'd hate for it to run out, Ada.
Explanation:
Thomas is transporting a shipment of opium for the Chinese.
We are the ones who make sense of it. All we know is that the brain truly believes the experiences that we feel. It's function is to interpret a hallucination as if it were real.