The introduction to Hegel's lectures on the philosophy of world history is often used to introduce students to Hegel's philosophy, in part because Hegel's sometimes difficult style is muted in the lectures, and he discourses on accessible themes such as world events in order to explain his philosophy. Much of the work is spent defining and characterizing Geist or spirit. Geist is similar to the culture of people, and is constantly reworking itself to keep up with the changes of society, while at the same time working to produce those changes through what Hegel called the "cunning of reason". Another important theme of the text is the focus on world history, rather than regional or state history.