Schopenhauer’s parable of the porcupine in winter

Each individual porcupine, encased in its prickly armour, felt cold and isolated. So one cold winter’s day they crowded themselves very close together, so as to profit from one another’s warmth and companionship. But soon they stabbed one another with their sharp quills, which caused them to separate. The porcupines were driven backwards and forwards from one trouble to the other- and only after many failures and much pain, did they find and adopt an optimal distance at which they could most tolerably exist.