Therefore whosoever heareth these sayings of mine, and doeth them, I will liken him unto a wise man, which built his house upon a rock: And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell not; for it was founded upon a rock. And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand: And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it. (Matthew 7:24-27 KJV)
When Typhoon Morakot sweeped across Taiwan, I saw on TV the image of a building falling into the river like a shoe box after flood waters eroded its foundation. This is a house that is built on sand and cannot withstand the floods.
Morality without the foundation of truth is also like a house upon the sand. There are people who like to avoid religion and just preach moral values by itself. Such moral values may be a beautiful house with marbles and chandeliers and lovely interior decoration, but its foundation is built on sand. When the floods come, it will fall into the river.