The 18th century in Europe is typically seen as the century of the Enlightenment. The Enlightenment is typically described as a time in which the world view of the average European changed and came to be based more on reason, science and optimism about the human condition than it had been before.
When we talk about the European world view, we must realize that we are making a huge generalization. Not all Europeans saw the world in the same way and not all of them changed their world views in the 18th century. We must also realize that the Enlightenment did not happen all of a sudden when the 18th century began. Instead, ideas like those of the Enlightenment had been around a long time before 1700 and ideas from before the Enlightenment persisted among some people long after 1700. However, historians do generalize and say that the European world view changed in the 1700s.
Before the Enlightenment, the typical European world view was somewhat pessimistic and was based on faith. People thought that the world could not be changed for the better because human beings are sinful and cannot be changed. People also typically looked to religion to try to explain how the world worked. They would say that things happened because they were the will of God. If their religion told them something that did not make sense to them, they did not try to use reason to question it. Instead, they took the truth of the religious teachings on faith. This changed during the Enlightenment.
During the Enlightenment, more Europeans came to believe in the ideas of science. They started to look to science to answer their questions about how the world worked. They started, for example, to look for natural causes of diseases rather than thinking that diseases were sent by God. They also started to think that they should use their reason to question things that did not make sense. As they started to think in these ways, they became more optimistic. They began to think that they could use science and reason to make the world a better place.
Thus, we can say that European world views changed in the 18th century. The old world view had been pessimistic and based on faith while the new was optimistic and was based on reason and science.