From: Middle English, from Anglo-French or Latin; Anglo-French, espirit, spirit, from Latin spiritus, literally, breath, from spirare to blow, breathe
Date: 13th century
1 an animating or vital principle held to give life to physical organisms
2 a supernatural being or essence: as Holy Spirit or Soul
4 the immaterial intelligent or sentient part of a person
5 a: the activating or essential principle influencing a person
Hexham's Concise Dictionary of Religion
In some religions, spirits are disembodied entities that display the characteristics of individual persons, and are sometimes regarded as the souls of dead ancestors. Spirits can interact and even communicate with the living through dreams, illness, and unusual events which reveal the presence of a spirit. The soul is the immortal element in human beings sometimes regarded as our true self. The immortality of the soul gradually replaced the earlier emphasis in early Christianity that the central concept was the resurrection of the body.
One may assume that the human brain is the seat of information collection and processing and that the glandular system contributes much to our emotional responses. Does anything remain unaccounted for in that system of human physiology, requiring the presence of an immaterial sentience essential for personhood? If so, do we interact with other humans, other sentient beings, even inanimate objects in ways that do not occur on the material plane of measurable observation?
In recent years, thinkers such as Jung have postulated a collective unconsciousness based on the occurrence of acausal coincidence, and that some level of deep meaning exists in universal symbols and human archetypes as revealed in mythology. Others argue that the search for meaning and significance where none exist gives rise to pseudoscience and undocumentable paranormal practices.
Atheist Definition: Spirit describes those essential elements of individual identity that are immaterial and do not, therefore, adhere to physical or medical laws. An individual’s spirit may interact with others, or with all existence (Spiritus Mundi, the spirit of the world) in ways that may reveal shared experience or common affect from which one may glean meaning. If one is concerned with the association with Spiritism, then the word perhaps may be used interchangeably with the terms "mind" or "soul."