A manager argued that he could either increase his business unit's margins or its sales, but not both. His chief executive reminded him of the time when people lived in mud huts and faced the stark choice between light and heat: punch a hole in the side of your hut and you let the daylight in but also the cold, or block up all the openings and you stay warm but sit in darkness. The invention of glass made it possible to overcome the dilemma—to let in the light but not the cold. How then, he asked his manager, will you resolve your dilemma between no sales or no margin improvement? Where is the glass?