One tends to project one's complexes on people, situations, things. What Jung calls shadow is that aspect of one's unconscious which contains the debris of one's inherent characteristics that gets repressed while adjusting to immediate social needs, in creating an amiable persona in other words. It is inevitable, and many a therapists today belonging to different schools may explain it less dramatically but the idea remains the same at the core. Freud may not have approved of Jung's terminology, and so do many recent analysts, but as a metaphor, as an idea of a stranger lurking within us, the symbolism intrigues me, as does many of Jung's ideas. The challenge of depth psychology is to release the gold that hides in the shadow, the creative energy that remains trapped in hazy clouds of repressions and associations. Neglect the shadow, run away from that which bothers you, and your true potential remains unrealized. Simple.
What Johnson argues, via Jung, is that:
The civilizing process, which is the brightest achievement of humankind, consists of culling out those characteristics that are dangerous to the smooth functioning of our ideals. Anyone who does not go through this process remains a "primitive" and can have no place in a cultivated society. We all are born whole but somehow the culture demands that we live out only part of our nature and refuse other parts of our inheritance. We divide the self into an ego and a shadow because our culture insists that we behave in a particular manner. Culture takes away the simple human in us, but gives us more complex and sophisticated power.
The only way shadow can manifest, unless you are conscious of it, is through projection. That is, it is neatly laid on someone or something else so we do not have to take responsibility for it. Hermann Hesse, ever a Jungian, wrote:
If you hate a person, you hate something in him that is part of yourself. What isn't part of ourselves doesn't disturb us.
That is projection. A conscious attempt to act out the shadow is a primary thing that can keep one more aware of the inner filth. In an interview Slavoj Zizek mentioned that whenever he meets his friends, they talk crass, untoward things with one another, referencing each other's mothers and all sorts of intimate things. Once satisfied, they agree that they have given a tribute to the filth and move on to much richer and nicer conversations. I am sure he won't think of it as acting out the shadow, but in my mind I see the metaphor at work.
The book aims for a more spiritual purpose eventually. Going beyond the contradictions provided to us almost daily by the mere process of living, that which shadow feeds on, one can move towards learning to see the contradictions as paradox, as something one accepts as the fact of life without trying to choose either this or that, and an answer for an individual, if there is one, emerges from there. Think of a Zen Koan that tells you to listen to the sound of one hand clapping. Its a paradox. Jungian system of individuation has similar aims that any spiritual system has, and he is often discarded as a mystic, but there is a metaphorical richness in his ideas vis-a-vis the psyche that provides an explanatory framework for the religious way of life.
Call it wholeness, totality, union of opposites, or the world navel, it is paradox that paves the way. The fish symbolism of Christ (also known as ichthys) has two intersecting arcs, leading to an acceptance of opposites as a whole, not weighing one over the other, like yin-yang, or the Mandala representing the Self (the whole-making principle in the psyche). It is this territory which is at odds with the neurosciences and the Freudian therapy, and relies heavily on symbols (dreams, active imagination).
Off course, one learns to "not" project the shadow on their own (like paying tribute to the filth), to learn and transform from one state to another, to be more broad-minded than before, to be more accepting of the world, without knowing all the above. But it is a complete system Jung provides that keep the more imaginative ones on a path, folks who think of personality as something that can be made whole again, like alchemists looking for inner gold.