Find a watch on a heath, and you assume a watchmaker
William Paley argued that stumbling on a watch in an empty field, with its intricate, purposeful parts, would force you to infer a maker, unlike a stone that could plausibly have always been there. He argued living things show the same signs of intricate design, and so must likewise imply a designer. The analogy became one of the most famous, and most contested, arguments for God's existence.