In Spain, many residents take a break during the middle of the day which is referred to as a 'siesta'. Taking a siesta leaves those to be re-energized to complete the rest of their tasks. Therefore, it is important to take a siesta.

First sentence is context. The second sentence is the premise. The last sentence is the conclusion.

@Derekt19 to add to this, in the assumption that tigers aren't mammals that still doesn't negate the main argument for why mammals shouldn't be kept as a pet. The main point of the conclusion is that they are aggressive and therefore unsuitable, but a tiger is just an example (any mammal can be replaced for because of their aggressive behavior). That is why targeting the main point of aggressiveness weakens the argument more, because it showcases that even violent mammals can still be kept as a pet. So it's not really 'outside knowledge' per-say but more about seeing what part of the conclusion can be used to best weaken the argument (looking at it from a different perspective).