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The echo principle
One of the most remarkable mysteries of nature is the bat. These strange creatures fly miles underground, swooping through dark caverns, yet they never strike the walls.
Until recently, we did not know how they did it. Scientists captured a group of bats to conduct some experiments with them. The scientists stretched wire across a long room and sent the bats through it. They never struck a wire. The scientists blindfolded the bats, thinking that maybe they were able to see in the dark. When the blindfolded bats were sent through the room, they again flew with perfect precision, never touching the sides of the room or the wires stretched across them.
When the mouths and ears of the bats were taped shut, different results were seen. With their eyes wide open, the bats crashed into both wires and wall. Further investigation revealed that the bats sounded a high, shrill note when they started to fly. The highly sensitive ears of the bats were receivers for the echoed sound. What they sent out came back to them. The echo principle became the tool for the flight of the bats.
The Bible repeatedly declares that the echo principle is a basic fact of life. The writer of Ecclesiastes said, “Cast your bread upon the surface of the waters, for you will find it after many days” (Eccl. 11:1, NASB). Jesus told His disciples, “By your standard of measure it shall be measured to you” (Mark 4:24). Paul declared to the Galatians, “Do not be deceived, God is not mocked; for whatever a man sows, this he will also reap” (Gal. 6:7).
Our lives are lived every day by the echo principle. Whatever we send out comes back to us in one way or another—it comes back to haunt us, or it comes back to bless us.
 Lewis, B. (1991). And Then Some …. Christianity Magazine, 8(7), 8.