Our true nature is always hidden. In order to protect our inner self we each present an image or personality in public which meets the expectations of others. This ‘mask’ also determines how we see ourselves. However, there are parts to our personality which we do not recognise, parts which are unconscious. These could be raw desires and emotions or thoughts and experiences which we are too ashamed to admit to. These will likely be dark aspects of our character which have been rejected or repressed due to our upbringing, or a disapproving society. Jung described this side of the personality as the shadow.

The shadow is an archetype, meaning that it exists in all of us. The shadow contains everything denied and despised, everything considered sinful and everything we find awkward or unnerving. Although the shadow is thought of as the dark side of the individual it should be noted that it could also contain undeveloped positive parts. Jung believed the shadow to be inferior and primitive in nature. Therefore since it is instinctive it is likely to have a disturbing influence on the personality of the individual unless it is confronted.

However, the shadow is difficult to perceive consciously. Since an individual will deny or ignore his or her shadow side, it is likely that it will be projected onto others. Instead of acknowledging their shadow the individual will unconsciously see it in people they encounter or even concepts, objects, ethics or groups. For example, the individual may find that they despise a specific person (or certain characteristics of that person) for no apparent reason. Where this hatred is emotionally obsessive, an irritation or an overreaction - where the emotions take control whenever this person is in close proximity - then it is likely the individual has stumbled upon parts of his or her own shadow. These characteristics that we find hideous in other people could in fact be our own repressed attributes. The shadow is most likely to infiltrate when the individual is tired, irritated or harassed.

The shadow is also encountered in dreams. It can be held accountable for the unpleasant thoughts or actions that seemingly violate the morality of the dreamer. The shadow may present itself as an unknown individual usually of the same sex as the dreamer. Equally, an unlikeable person who is known to the dreamer could also represent the shadow.