My favorite Sci-Fi movie is "Forbidden Planet," made in 1956. It was decades ahead of its time. The famous Star Wars series made extensive use of ideas borrowed from "Forbidden Planet." The movie's quintissential robot named "Robbie" was used for years by various TV shows and series. In this sci-fi classic, a spacecraft travels to the distant planet Altair IV to discover the fate of a group of scientists sent there decades earlier. When Commander John J. Adams (Leslie Nielsen) and his crew arrive, they discover only two people: Dr. Morbius (Walter Pidgeon) and his daughter, Altaira (the beautiful Anne Francis!), who was born on the remote planet. Soon, Adams begins to uncover the mystery of what happened on Altair IV, and why Morbius and Altaira are the sole survivors.
Adams learns that the original inhabitants of the planet, the Krell, were on the brink of commissioning an amazing supercomputer that would allow their thoughts to be projected and physically manifested anywhere on the planet. The machine occupied thousands of square miles underground and harnassed incredible amounts of energy. Imagine that! Just think about something and shazzam! There it is for real!
But the Krell forgot about the evil thoughts that lie hidden in our subconcious minds - things like jealousy, anger, and unforgiveness. So, while they slept on the first night after commissioning their new supercomputer , their uncontrolled evil subconscious thoughts were physically manifested by the supercomputer as real-world monsters who killed everyone on the planet before sunrise. Fast forward: Morbius feels threatened when his daughter Altaira falls in love with the crew captain from Earth. Every night when Morbius sleeps his resentment towards the crew from Earth is manifested by the Krell supercomputer as an invisible monster who begins to attack and kill members of the expedition from Earth. But neither Morbius nor the crew from Earth understand that the monster is coming from Morbius' subconscious mind ... until the climax of the story. (If you're in a hurry, fast-forward the video clip to 3:00 minutes.)
Summary - The Krell didn't understand how evil their hearts were until their evil was manifested in physical form by their incredible supercomputer. And God's Word repeatedly warns that we don't understand how evil our hearts are either!