The term "art of mind" could be interpreted in various ways depending on the context. However, if we consider it as the ability to create, imagine, and think creatively, then the antonyms could be stagnation, rigidity, and inflexibility. These traits represent a lack of imagination, creativity, and innovation. Another antonym could be dullness, which means lacking energy, interest, or excitement. The art of mind implies a lively and imaginative mind, whereas dullness represents a lack of enthusiasm, imagination, and creativity. Therefore, to develop the art of mind, one may need to cultivate traits such as flexibility, creativity, innovation, and enthusiasm.