Short answers, pulled from the story.
The soul is the immaterial aspect or essence of a living being. It is typically believed to be immortal and to exist apart from the material world. Anthropologists and psychologists have found that most humans, across cultures, believe in a soul or spirit and distinguish it from the body and the mind.
Buddhism teaches anatman, or not-self, holding that there is no permanent soul. The idea of an unchanging soul conflicts with dependent origination and the impermanence of the five aggregates, since everything arises and dissolves. In Milinda's Questions, the monk Nagasena argues that a person is like a chariot, only a conventional label for a collection of interdependent parts.
Plato considered the soul the eternal, incorporeal essence of a person, divided into three parts: logos in the head, thymos near the chest, and eros in the stomach. Aristotle defined the soul as the first actuality of a naturally organized body and argued against its separate existence, treating body and soul as matter and form. Aristotle discussed the soul in his work De Anima.
The English word soul stems from the Old English saawl, with the earliest attestations in the Oxford English Dictionary dating to the 8th century. It is cognate with Old Frisian sele, Gothic saiwala, Old High German seula, Old Saxon seola, and Old Norse sala. Present-day cognates include Dutch ziel and German Seele.
Islam uses two terms, ruh for the divine spirit or breath of life and nafs for a person's disposition, with the Quran describing the commanding self, the accusing self, and the tranquil self. Judaism uses terms such as nefesh, ruach, neshamah, chayah, and yechidah, and Kabbalah maps these onto five soul elements. The Hebrew scholar Robert Alter rejects soul as a valid English translation of the Hebrew Bible.
In 1901, the physician Duncan MacDougall of Haverhill, Massachusetts, weighed six dying patients on an industrial-sized scale to test whether the soul had weight. One patient lost three-fourths of an ounce, about 21.3 grams, at the time of death, leading him to conclude the soul had weight. The physicist Robert L. Park and the psychologist Bruce Hood later judged the experiments unscientific because the weight loss was not reliable or replicable.