After this philosophical golden age other systems appeared, like Cynicism, Stoicism, Epicureanism and Skepticism. Aristotle said that Thales was the first to consider the basic principles and the question of the originating substances of matter and, therefore, the founder of the school of natural philosophy. Greek philosophers were among the first in the West to explore nature in a rational way and to make educated guesses about the creation of the world and the universe. This is why Greece is often referred to as the birthplace of Western culture.