Many, many years ago, there was a group of people who made swimming pools. They made great pools. Many people flocked to these swimming pools they built and found refreshment from the blistering sun and relief from the toil of their lives with a simple dip.
The swimming pools were designed in all sorts of ways- some rustic, some modern, some square, some circle. But they all, at the end of the day, provided a structured foundation where water could be filled (and stay) for the benefit of all who wanted to partake.
The pool builders, as the years went by, wanted to make sure their pools were even better, so they made all sorts of new shapes and styles. They worked extremely hard on making sure the foundation was strong and beautiful. And they accomplished it. As the years went by, new generations of pool builders came and went, and many pools were scattered throughout the land. Over time, however, the pools were still structurally sound, but the pool builders just put in a little less water. Their kids used just a little less, and theirs still a little less.
One day, a pool builder noted that for many, many years, the pools that they had been building had no water in them. They built structurally sound, beautiful pools, but there was no water in them. He went to his fellow pool builders and said, "Hey, did you know these things are supposed to have water in them?"
The other pool builders said in reply, "Oh we know. It rains sometimes and the rain gathers. And the water stays, for several days sometimes."