Three men were once fishing in the middle of a lake. Suddenly, the oldest of the three jumped up and said, "I forgot my tackle," whereupon he got out of the boat, promptly walked across the top of the water to the shore, found his tackle and returned again, walking on top of the water. After while, one of the other fisherman jumped up and said, "I forgot my bait," and he also left the boat and went across the lake to the shore and back, walking on top of the water. After a bit the third man, a young and inex-perienced fisherman, jumped up and said, "I forgot my lunch." Since the other two had walked across the lake on top of the water, this young man boldly stepped out of the boat and promptly sank. One of the older fishermen said to the other, "Do you think we should have told him about the rocks?" When you don't know, ask.