Auguste Comte’s theory of the development of the human spirit is interpreted as supporting a vision of linear, ascending movement, aiming at a positive stage. Given this, the exegesis is focused, mainly, on the notion of progress. In this paper, I discuss the notion of decline, the counterpart of the preferred notion, which I consider to be essential for the above-stated pursuit of the human spirit. This notion has received less attention than the positive one of progress, and my goal here is to highlight the strengths and the function of the notion of decline, paying attention to the similarities that can be established between Comte’s “decline” and the corresponding notion from Brentano’s theory of the four phases.