The soul is the name given to the supposed immaterial part of an individual, which some believe can exist separately from the body in the afterlife. It's considered by those who believe in it to be a self evident and intrinsic part of humanity. It is an important aspect of much religious thought, particularly when concerning the afterlife.
The concept of the soul it is not recognized by science because it is both non-falsifiable and supernatural. The soul is postulated by believers to be completely immaterial. Scientists who attempt, and without exception fail, to find evidence of the soul (see Weighing the soul below) will usually be told that they can't measure or characterise it anyway. Like other beliefs of its kind, this makes the idea of the soul somewhat immune to scrutiny because believers can always turn around and play this particular card against soulless scientists. This is considered odd among scientists and disbelievers in the "soul" because if something can't be measured or tested -directly or indirectly- in any way, then it can't affect the material world and therefore is, in all practicality and in all actuality, non-existent.
Many people do still refer to the soul in a metaphorical sense without thinking of something magical and immaterial.
Scientific evidence against the existence of soul
The soul is usually described as an immaterial "thing" in a way that implies that it contains someone's consciousness, personality, personhood and memories. After all, what would be the point of a soul surviving death, if it doesn't think or have any memory?
Neuroscience suggests that consciousness is strongly dependent on the brain and there have been many cases where profound personality change followed brain damage. Phineas Gage was one example whose personality changed radically after brain damage, . Another person developed uncontrollable paedophilia at two times which correlated with specific brain tumours. . Bilateral damage to the amagdala prevents humans reacting when their personal space is violated. Amagdala damage to monkey mothers leads to reduced maternal care for their infants.   Psychoactive substances can be used to temporarily alter the mind through manipulation of neurotransmission. Also, lobotomy changes personality.
Below are examples where the condition of the brain affects consciousness:-
- Brain damage
- Electrode stimulation
- Transcranial magnetic stimulation
- Split brain patients
The condition of the brain clearly affects consciousness and personality during life, therefore skeptics suggest consciousness is unlikely to survive the complete cessation of brain function at death.
History of the Hebrew / Christian concept
Before the influence of the Greek concept of the psyche on Hebrew thought, the bible's authors only spoke of a man having breath (spirit), and any living creature was called a "soul". In fact, the belief in consciousness after death was explicitly denied in the Old Testament. Ecclesiastes 9:5: "For the living know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten."
Even the New Testament speaks only of a promised resurrection of the dead at the end of time, with two notable exceptions: Jesus relates a parable of a rich man burning in hell, and later on the cross Jesus says to the Good Thief, "I say to you, this day you will be with me in Paradise".
The former was a parable which was intended to convey what Christians consider a truth about the need to convert before death and judgment, not necessarily to convey actual conditions in the afterlife. The latter can be explained by the fact that the original Greek text did not use commas, so the insertion of the comma after the word "you" was an arbitrary choice of the translators. If the comma is moved, the passage then reads "I say to you this day, you will be with me in Paradise" which allows for the traditional understanding of a bodily resurrection at the end of time rather than a disembodied state immediately after death.
In this sense it is similar to: "Woman without her man is an animal." and "Woman, without her, man is an animal." You make your arbitrary choice and chose the meaning that appeals to your existing beliefs.
Weighing the soul
In an effort to put the soul onto a more scientific footing, Dr. Duncan MacDougall of Haverhill, Massachusetts tried, in 1901, to weigh the soul. He took a dying man and weighed him until the moment of death at which point he apparently noticed a reduction in weight of three fourths of an ounce. He subsequently repeated the experiment with fifteen unfortunate dogs and found no such reduction.
Over time he repeated the experiment with five other dying humans - and got a variety of differing results which rather invalidated his premise.
Harry La Verne Twining also attempted to weigh the soul of animals in a set of experiments and obtained some interesting differences in weight loss. However scientists including Twining himself later on in his life claimed that the experiments turned out to be the result of a natural cause, namely moisture loss.
Famous mangled quotes
- "Soul is the brevity of wit."
- Harlow (1868), pp. 339–342.
- "Brain tumour causes uncontrollable paedophilia"
- Eagleman, Philosophy Bites Podcast, "David Eagleman on Morality and the Brain"
- Kennedy, DP; Gläscher, J; Tyszka, JM; Adolphs, R. "Personal space regulation by the human amygdala." (2009). Nat Neuroscince. 12 pmid=19718035
- Bucher, K.; Myersn, R.; Southwick, C. "Anterior temporal cortex and maternal behaviour in monkey." (1970). Neurology. 20 pmid = 4998075
- snopes: Soul Man
- Len Fisher Weighing The Soul: Scientific Discovery From the Brilliant to the Bizarre 2004, p. 14-15