One definition for spirituality is, "the concept of an ultimate or alleged immaterial reality; an inner path enabling a person to discover the essence of his/her being." Therianthropy itself is not a spirituality or religion. It is an identify phenomenon in which a person identifies partially or in whole as a non-human animal. Physically, Therianthropes are human and understand that they have human bodies. In general, those who identify themselves as Spiritual Therianthropes believe that they are an animal on a spiritual level. Being a Spiritual Therian usually does not interfere with or conflict with another spiritual or religious belief. Therianthropy is often incorporated into other beliefs. For example, there are many Christian Therians in the community.
The online Therian community began on Alt.Horror.Werewolves in 1993. The majority of Therians from that time classified themselves as spiritual. Though there were discussions about the psychological changes that take place during shifts.
Therians don't know what causes them to identify as non-human. Therianthropy is a subjective belief based on personal experiences and not on scientific fact. Therefore, both Spiritual and Psychological Therianthropes are legitimate and acceptable in the community because they have similar experiences such as shifts and have one or multiple theriotypes. Many Therians explain their identity through both spiritual and psychological causes.
- See also: Psychological Therianthropy
There are multiple spiritually related causes found in the community for why people label themselves spiritual Therianthropes.
Possible Causes for Spiritual Therianthropy
(This list may not be exhaustive.)
- Multiple Parts of the Self/Soul
- Misplaced Soul
- Dual Souls
- Link to Nature
- Reincarnation/ Past Lives
- Other Spiritual Causes
Multiple Parts of the Self/Soul
Some spiritual beliefs consist of souls having multiple layers or components. Together, the parts are the whole self, and the soul remains that way throughout life. The Ancient Egyptian concept of the soul  and Norse beliefs  are good examples. The concept is that one or many of these components of the self, whether it be personality, the mind, the inner self, or another component, can have the nature of an animal. Some parts are still human. This is not the same as having a soul which has been reformed from the pieces or shards of many different souls. The belief in reincarnation is not necessary to this explanation for spiritual therianthropy.
This can be similar to or in conjunction with reincarnation, but some Therians have alternate explanations. A belief in a previous life is not always the case. Therians often have the feeling that they are not in the correct physical body. This has lead many to believe that an animal spirit was placed into the wrong body as a spiritual or cosmological mistake. If a Therian believes in a deity/deities they may think the deity/deities placed an animal soul within them for various purposes, ranging from a joke learning opportunity for the sou.
It's believed by some that two or more souls could occupy the same body. If one or more of the souls is animal instead of human, this could cause a person to identify as non-human. Again, a belief in a previous life is not always necessary. Having more than one soul occupy a body may be a new development, and it does not hinge on the belief of reincarnation or a previous life.
Link to Nature
This is the concept that Therians are a link between the human and animal worlds and the earth. We are a needed connection to a more primal side of humanity. This might also include the belief that nature, a deity or deities, or other power gave us animal souls in an attempt to balance the world. The balancing might take place because Therians feel the need to fight for and protect the environment. The belief in reincarnation and a previous life is not required. This is similar to the concept "Links to Gaia" written by Meirya in 2006. 
Reincarnation/ Past Lives
Reincarnation seems to be the main spiritual cause for why Therians identify as non-human. Simply put, this is a believe that the soul, upon death of the physical body, finds another body to inhabit.   For Therians, this means that a person was an animal in a previous life or multiple past lives. It is thought by some Therians that having been an animal in a past life has altered the nature of the soul's energy or vibration which thus has an impact on their current life and identity. The animal soul that now inhabits the human body may cause shifts, during which behaviors are more animalistic and instinctual. Not all Therians have memories of these past lives as animals, but some can recall them.
Other Spiritual Causes
The following causes may be lesser known, not discussed as often in the Therian community, or of a controversial nature.
Walk-in souls are souls who choose to incarnate into an established body rather than a newborn infant. The original soul that inhabited the body returns to the spirit realm. Sometimes the two souls can inhabit the same body during a transition period. Some people believe that the walk-in can be permanent or temporary, and that the original soul sometimes returns. Walk-in events cause a person to feel as if they are in the wrong time and place, in the wrong body, or maybe even on the wrong planet. 
However, in the article, "Are You a Therian?" written by Strill,  Walk-ins are not considered to be Therianthropy because the new soul is an outside source. The event is more like a possession. The possibility of a walk-in being temporary also disqualifies it from being Therianthropy, which is a permanent part of a person's identity.
Unlike a soul which originally was multiple parts, soul shattering or splitting can occur while the soul is outside or inside of a physical vessel. This can occur because pieces of a soul need to learn or have certain experiences to continue their spiritual growth. Or it could happen because of traumatic events. Sometimes, the soul pieces are not human, but when they join with parts of a human soul, it can result in a person identifying as a Therianthope because they feel non-human.
In the Otherkin community, soul shards seem to mainly refer to identifying as a divine being or an incarnated deity. However, this seems to have just been the personal beliefs of a few individuals. This concept was likely picked up and spread by other people on Tumblr who have not completely understood or researched the concept of soul shards. 
In many spiritual beliefs and practices, a soul shard is a lost piece of one's self. the splitting of a soul and the resulting shards are considered unhealthy and are indications that a soul retrieval is required. A soul that has been shattered and that needs healing is often indicated by depression, addictions, or prolonged physical illness. Soul retrieval may be able to help bring balance and health back to a person's life.  
Psychic Connection to an Animal
This is the belief that a person has taken on the mind of an animal that they were very close to an formed a strong psychic link to. In a sense, the person becomes that animal. This connection could be related to knowing that animal in a past life as well.
However, does having a psychic connection to an animal make a person a Therianthropy? It might be possible for anyone to develop their psychic or empathetic abilities and be able to form connections with animals. Choosing to take on the mentality of an animal does not make a person a Therianthrope. The animal which a person has a connection to is often still living and independent, therefore it can't become a person's identity.  
- ↑ "The Ancient Egyption Concept of the Soul", Michigan State university, Department of Antrhopology, October 27, 2014. http://anthropology.msu.edu/anp455-fs14/2014/10/27/the-ancient-egyptian-concept-of-the-soul/ Egyptian Religion, Encyclopedia Britannica Online, https://www.britannica.com/topic/ka-Egyptian-religion
- ↑ Dan McCory, "The Parts of the Self", Norse Mythology for Smart People, 2012. http://norse-mythology.org/concepts/the-parts-of-the-self/
- ↑ Meirya, 2006. "Otherkin and Therian Theories of Cause or Origin" Hosted on Project Shift. http://project-shift.net/otherkin-therian-theories-of-cause-or-origin/
- ↑ Reincarnation. Dictionary.com http://www.dictionary.com/browse/reincarnation
- ↑ Buddha Dharma Education Association & BuddhaNet, Takashi Tsuji, 1996, "On Reincarnation" http://www.buddhanet.net/e-learning/reincarnation.htm
- ↑ "Walk-in Souls About Souls that Swap Places" By Phylameana lila Desy, April 18, 2016. http://healing.about.com/od/spirituality/a/walk-in-souls.htm
- ↑ Crystalinks, "Walk-in Souls" http://www.crystalinks.com/walk_ins.html
- ↑ Strill, "Are You a Therian?", July 2008. http://project-shift.net/are-you-a-therian/
- ↑ Sacred Liminality, musings of a genderfluid Fae. https://sacredliminality.wordpress.com/2015/08/22/glossary-of-terms/
- ↑ Sopherielspeaks, "Shards and Projections" August 11, 2014. http://sopherielspeaks.tumblr.com/post/94434358093/shards-and-projections See also: http://sopherielspeaks.tumblr.com/post/94357296898/journey-so-many-times-now-i-feel-like-thats-all
- ↑ Cipher, May 4, 2016, " Guide to Spiritual Otherkin" http://lucifer-and-chill.tumblr.com/post/139689383904/guide-to-spiritual-otherkin
- ↑ Soul Retrieval by Sandra Ingerman, 2007. http://www.sandraingerman.com/soulretrieval.html
- ↑ "Shamanic Soul Retrieval and the Lies of the Greedy" BY ANDRIEH VITIMUS. http://magicblog.andriehvitimus.com/2013/01/shamanic-soul-retrieval-and-lies-of.html
- ↑ Savannah Eve, August 16, 2013. "Talking to Animals, The Psychic Connection" http://hubpages.com/animals/Talk-To-The-Animals
- ↑ "Psychic Connections with Animals" Crystal Links. http://www.crystalinks.com/animalpsychic.html