The earliest illustrations by humans on cave walls were likely made from directly observable phenomena. The Egyptians made a conceptual leap with their ability to artistically represent abstract ideas, such as their pantheon of gods. Before the scientific revolution began around 1500, priests, astrologers, alchemists, and philosophers all claimed to have the answers to the workings of the universe. One might argue that in illustrations of real or imagined experiences one can find a broader understanding of the natural world and the final causes of all things.