Here is a quote which even after all the decades of studying never loses its appeal and instead only grows stronger:
"Insofar as the archetypes act upon me, they are real and actual to me, even though I do not know what their real nature is. This applies, of course, not only to the archetypes but to the nature of the psyche in general. Whatever it may state about itself, it will never get beyond itself. All comprehension and all that is comprehended I in itself psychic, and to that extent we are hopelessly cooped up in an exclusively psychic world. Nevertheless, we have good reason to suppose that behind this veil there exists the uncomprehended absolute object which affects and influences us...."