The Great Wall took endless number of lives away to be built. If you think further, you'll find it's not just the human body that enabled the Great Wall to exist now, but something else of them. All the labor out of technology, ones who directed them, ones who designed the structure, and one who made the final decision to build it, are the very existence to have made the Great Wall. Which part of their body actually did those activities? We can call it as Spirit.

Spirit generates meaningful actions out of your body. Without it, our existence wouldn't go beyond a few animals living in social networks. Spirit is not something down to our physical or emotional existence, but upto high level decision making and all the required functions to reach the decision.

In chinese, they call it 'jing shen', which means 'elaborative god'.