Not all components of the psyche show development, but many of them do, and those developmental aspects or stages need to be taken into account. They are not the whole story of the psyche, but they are an important part. We live in an evolutionary universe, and those currents of evolution appear to operate in the human mind as well. These developmental stages appear to be concentric spheres of increasing embrace, inclusion, and holistic capacity. The Great Chain is perhaps a misnomer.
Some modern thinkers accept the existence of matter, body, and mind, but reject soul and spirit.
They therefore prefer to think of the levels of consciousness as proceeding from, for example, preconventional to conventional to postconventional. That these levels, nests, or waves are arranged along a great rainbow or spectrum does not mean that a person actually moves through these waves in a merely linear or sequential fashion, clunking along from body, then to mind, then to soul, then to spirit. Those are simply some of the basic levels of consciousness that are potentially available.