  According to Du Bos, all arts are imitative, but the arts do not all represent in the same way. In the course of the Critical Reflections, Du Bos makes a contribution to philosophy of language by distinguishing between natural signs and the artificial signs found in language. Natural signs, such as those found in painting, sculpture, and music, represent because they resemble their objects. The artificial signs of language are arbitrary or conventional. They are employed in poetry (that is, literature).