The challenging ideas technique is about questioning a person's authority, belief, idea or opinion, often by exposing a contrary idea, or making a rhetorical question. In the discussion, this is what Salim uses as he questions Bekak's opinion of what the truck represents. Salim expresses a different and contrary thought to Bekak's, for Salim, the truck does not represent freedom to the delivery driver as he hates his job, and thus, the truck is more of a prison to him.
