The Vocation of Man is the author's way of trying to explain the true purpose of all human beings.
Fichte divides the book into three parts: "Doubt," "Knowledge," and "Faith." In the first part, the author argues that human beings lie to themselves by thinking that they have free will; people act because they are subject to the laws of cause and effect. For the second part, "Knowledge," the author talks about natural existence and how human beings shape their reality through what they know. In the final and perhaps most important part, the author talks about faith.
Human beings are guided by a higher power beyond themselves, he argues. The spirit gives people hope. Therefore, serving God and doing everything according to God's will should be the ultimate purpose of every human being, even if they have to go through suffering when they do it.