Many ancient Greek philosophers were suspicious of emotions, believing that reason was the key to freeing the mind from destructive, distracting impulses. However, the 18th-century Dutch philosopher Baruch Spinoza, and later Charles Darwin, came to the conclusion that emotion and reason work in tandem to help us survive and build important social bonds – a theory that was later confirmed by modern psychologists and brain scientists. This short video from Scientific American explores how emotions transformed from nuisances to necessities in the eyes of Western philosophy and science – with puppets!