Carl Gustav Jung (1875 to 1961) was a Swiss psychiatrist and close colleague of Dr Sigmund Freud. Jung broke from the Freudian psychoanalysis school of thought, over the issue of the unconscious mind as a reservoir of repressed sexual trauma which causes all neuroses. Jung founded his own school of analytical psychology. Jung's approach to psychology has been influential in the field of depth psychology and in countercultural movements across the globe.

Jung is considered as the first modern psychologist to state that the human psyche is "by nature religious" and to explore it in depth. He emphasized understanding the psyche through exploring the worlds of dreams, art, mythology, religion and philosophy. Although he was a theoretical psychologist and practicing clinician, much of his life's work was spent exploring other areas, including Eastern and Western philosophy, alchemy, astrology, sociology, as well as literature and the arts. His most notable ideas include the concept of psychological archetypes, the collective unconscious and most notably the phenomenon known as synchronicity.

Synchronicity
Jung created the term synchronicity to describe the alignment of "universal forces" within the life experiences of an individual. Jung hypothesized that many experiences perceived as coincidences were not merely due to chance, but instead reflected an ineffable alignment or connection of such forces, within the individual. Jung's belief was that, just as events may be connected by causality, they may also be connected by meaning. Events connected by meaning need not have an explanation in terms of causality. This contradicts the Axiom of Causality in specific cases but not generally.

Synchronicity implies that events are "meaningful coincidences" ...if they occur with no causal relationship, yet seem to be meaningfully related. Jung defined synchronicity as an "acausal connecting  principle" or as "acausal parallelism." He introduced the concept as early as the 1920s but gave a full statement of it only in 1951 in an Eranos lecture. Jung used the concept to address such phenomena as paranormal and/or psychic ability or perception.

The process of becoming intuitively aware and acting in harmony with these forces is what Jung labeled "individuation". Jung said that an individuated person would actually shape events around them through the communication of their consciousness with the collective unconscious.

Jung coined the term “collective unconscious” to refer to that part of a person's unconscious which is common to all human beings, as opposed to personal unconscious, which is unique to each individual. According to Jung the collective unconscious contains archetypes, which are forms or symbols that are manifested by all people in all cultures. The concept of collective unconscious relates to the Spiritual model of living beings consisting of individuated parts of Spirit encased in physical form...

Like an island in the sea we appear as distinct individuals, but beneath the surface we are all connected.

Archetypes
According to Jung's interpretation, archetypes are innate prototypes for ideas, which may subsequently become involved in the interpretation of observed phenomena. A group of memories and interpretations closely associated with an archetype is called a complex, and may be named for its central archetype (e.g. "mother complex"). Jung often seemed to view the archetypes as sort of psychological organs, directly analogous to our physical, bodily organs: both being morphological givens for the species; both arising at least partially through evolutionary processes. 

There are four famous forms of archetypes numbered by Jung:

1. The Self - the unification of consciousness and unconsciousness in a person, and representing the psyche as a whole.
    

2. The Shadow - every manifest part of ourselves has a
   repressed and opposite counterpart, represented by the shadow.
    

3. The Anima - feminine principal, a young lady, representing intuitive wisdom.
    

4. The Animus - the masculine principal, a handsome young man, representing active, assertive energy.

The symbols of the unconscious abound in Jungian psychology, eg: The Syzygy (Divine Couple), The Child, The Superman, The Hero, The Great Mother (manifested either as the Good Mother or the Terrible Mother), The Wise Old Man, The Trickster or Ape. Jung’s archetypes relate to the concept of occult symbols, ie ideas and images that have become charged with significance through aeons of reflection and veneration now standing ready to release their potential upon invocation. For example, Jung interpreted the Ouroboros or the snake biting its own tail, as having an archetypical significance to the human psyche. The Jungian psychologist Erich Neumann writes of it as a representation of the pre-ego "dawn state", depicting the undifferentiated infancy experience of both mankind and the individual child.

"There are no longer any gods whom we can invoke to help us. The great religions of the world suffer from increasing anaemia because the helpful numina have fled from the woods, rivers, mountains, and animals, and the God-men have disappeared underground into the unconscious. There we suppose they lead an ignominious existence among the relics of the past, while we remain dominated by the great Déesse Raison, who is our overwhelming illusion." 
 
"We are so captivated by and entangled in our subjective consciousness that we have simply forgotten the age-old fact that God speaks chiefly through dreams and visions."

"Whatever else the unconscious may be, it is a natural phenomenon that produces symbols, and these symbols prove to be meaningful."

"At a time when all available energy is spent in the investigation of nature, very little attention is paid to the essence of human-kind, which is psyche, although many researches are made into its conscious functions. But the really unknown part, which produces symbols, is still virtually unexplored. We receive signals from it every night (Dreaming), yet deciphering these communications seems to be such an odious task that very few people in the whole civilized world can be bothered with it. Humankind's greatest instrument, psyche, is little thought of, if not actually mistrusted and despised.

This modern standpoint is surely one-sided and unjust. It does not even accord with the known facts. Our actual knowledge of the unconscious shows it to be a natural phenomenon, and that, like nature herself, it is at least neutral. It contains all aspects of human nature... light and dark, beautiful and ugly, good and evil, profound and silly. The study of individual as well as collective symbolism is an enormous task, and one that has not yet been mastered. But at last a beginning has been made. The results so far gained are encouraging, and they seem to indicate an answer to many of the questions perplexing present-day humankind."

- Carl Jung