It is easy to confuse such questions -- for example , to argue that people eat because they 're hungry and not to acquire nutrients -- without realizing that the reason people experience hunger is because it causes them to acquire nutrients .
It is easy to confuse such questions -- for example to argue that people eat because they 're hungry and not to acquire nutrients -- without realizing that the reason people experience hunger ( causation ) is because it causes them to acquire nutrients ( function ) .