- This pseudo-Paper is intended as the mechanism to record time spent on the Note 'Dicephalus1' during my Thesis research, as from 2011.
- For the actual time recorded, click on "Paper Statistics" above.
Write-up2 (as at 13/05/2020 18:57:36): Dicephalus
- There are several related pathological conditions in which the number of animals and the number of individuals may fail to align. In sequence of severity of the “condition”:-
- Conjoined Twins: Wikipedia: Conjoined Twins. Varies from a fairly loose conjunction of individuals, who may be separated, to more severe forms with shared organs and limbs. This article is of interest not least because it discusses the issue of fission versus fusion, with the latter now the favourite suggestion.
- Craniopagus: Wikipedia: Craniopagus Twins. The babies are joined at the skull. Contrast the case where both twins are persons with the degenerate case Wikipedia: Craniopagus Parasiticus.
- Polycephaly: Wikipedia: Polycephaly. Animals or humans with apparently more than one head. Dicephaly is the limiting case. Usually an extreme version of conjunction. See, for example, BBC - Rare two-headed snake. Note that the description “two headed” seems more plausible in the case of reptiles than humans, given their presumed reduced mental experience. That said, given that dicephaly is – according to this article – a case of incomplete fission4 of an original single individual – this descriptive decision may be correct.
- Diprosopus: Wikipedia: Diprosopus. Animals, including humans5, with two faces. See:-
→ Guardian: Diprosopus (Sydney, 2014),
→ MedicalXpress: Diprosopus (Sydney, 2014),
→ Gulf News: Diprosopus (Sydney, 2014) and
→ Mail Online: Diprosopus (Sydney, 2014);
→ Mail Online: Janus Cat.
There may be one or two brains, but only one skull. The important thing – and what differentiates the diprosopus from the dicephalus – is that there is much less duplication of body parts, so it is very much two brains sharing one body – though it can also be the relatively superficial – though tragic – case of one brain, one body and two faces.
- All these situations – and in particular the paradigm case of dicephalus, wherein it appears that we have a (human) animal with two heads – are often cited as a prima facie problems for Animalism6.
- The claim is that while we have multiple persons7, we only have a single animal8, so the animalist claim that persons are numerically identical to their organisms9 is false.
- Of course, the above claim is somewhat bald. Animalism10 - at least in the form expounded by Eric Olson - has no truck with psychology as necessary for our persistence. While Olson often refers to “people” this is just shorthand for “some of us11”, rather than “persons”, the plural of person.
- So, if the animalist claim is that we are human animals, then the question is – in the case of dicephalus and related conditions – how many of us are present, and how many human animals are present. Animalism need the numbers to be equal.
- The cases under consideration have the advantage over standard Thought Experiments12, in that they are real-life cases. What is actual must be possible, and a standard argument against TEs is thereby avoided – namely that some of them, at least, whatever our intuitions may say, may not in fact be possible because the TEs are under-described.
- That said, there’s still a temptation to push the boundaries, and to consider cases in this general area that are not actual, yet are not quite as science-fiction as the usual TEs.
- Cases of dicephalus are fairly rare, and often one “twin” is degenerate (contrast Wikipedia: Craniopagus Parasiticus with Wikipedia: Dicephalic Parapagus Twins) so it’s not clear that we have two persons or two of “us”. However, the case of the dicephalus twins, Abigail and Brittany Hensel, where one body appears to be coordinated by two brains (see Abigail and Brittany Hensel, and probably more “official” sites – see Wikipedia: Abigail and Brittany Hensel for instance) shows that this is not necessarily the case. Here we definitely have two persons, but maybe only one animal. This is probably a real-life case of either incomplete fission13 or of fusion14.
- There are two issues with these cases:-
- How should they be best described?
- How should the animalist respond?
- I need to research this further, but it seems to me that we have a sliding scale of pathological cases – from that of Siamese twins (who are often fairly loosely connected, and can often be surgically separated) to the much more extreme cases of diprosopus.
- I presume, also, that we can have both fission and fusion.
- In the case of (incomplete) fission, the twins will be identical, as the situation is one where the twinning process has not completed.
- But (I imagine) we can also have a case of fusion, where the twin-embryos – whether identical or fraternal – that were separate have subsequently partially fused.
- The most likely response from the animalist is that the dicephalus is not a single organism, but two organisms that share some body-parts.
- The force of the arguments in this kind of case depends on “relevant similarity” – if the dicephalus-case is sufficiently similar to the general case, it can be used to show things about the general case. But this claim can be rejected.
- In the case of diprosopus, it is more difficult to claim that there are two organisms. Now – in practice – there are never two persons either (as all the 30-odd cases recorded since 1860, the condition has proved quickly fatal, so there are no persons present). But this might not always be so. So, Lynne Rudder Baker might claim that the rudimentary persons are indeed persons – as there is a possibility that they would develop into robust persons. Failing that, it might be the case in the future that there is a case where the diprosopus survives to develop personality.
- For a page of Links15 to this Note, Click here.
- Works on this topic that I’ve actually read16, include the following:-
- "Blatti (Stephan) - Animalism, Dicephalus, and Borderline Cases", Blatti
- "Blatti (Stephan), Ed. - The Lives of Human Animals", Blatti
- "Blatti (Stephan) - Animalism and its Implications", Blatti
- "Buchanan (Rachael) - The battle to separate Safa and Marwa", Buchanan
- "Hershenov (David) - Countering the Appeal of the Psychological Approach to Personal Identity", Hershenov
- "Liao (S. Matthew) - The Organism View Defended", Liao
- "Shoemaker (David) - Personal Identity and Immortality", Shoemaker
- "Shoemaker (David) - Personal Identity, Rational Anticipation, and Self-Concern", Shoemaker
- "Wilson (Jack) - Beyond Horses and Oak Trees: A New Theory of Individuation for Living Entities", Wilson
- A reading list (where not covered elsewhere) might start with:-
- "Barilan (Y. Michael) - One or Two: An Examination of the Recent Case of the Conjoined Twins from Malta", Barilan
- "Campbell (Tim) & McMahan (Jeff) - Animalism and the Varieties of Conjoined Twinning", Campbell & McMahan
- "Hershenov (David) - Problems with a Constitution Account of Persons", Hershenov
- "Hershenov (David) - Shoemaker's Problem of Too Many Thinkers", Hershenov
- "Koch-Hershenov (Rose J.) - Conjoined Twins and the Biological Account of Personal Identity", Koch-Hershenov
- "Olson (Eric) - The Metaphysical Implications of Conjoined Twining", Olson
- "Reid (Mark D.) - A Case in Which Two Persons Exist in One Animal", Reid
- "Snowdon (Paul) - Animalism and the Unity of Consciousness", Snowdon
- This is mostly a place-holder17.
- This is the write-up as it was when this Abstract was last output, with text as at the timestamp indicated (13/05/2020 18:57:36).
- Link to Latest Write-Up Note.
This doesn’t seem to explain why there should be two brains, however. An actual search of the Encyclopedia delivers a much briefer and less informative article.
- The Mail Online article quotes the following “Medical Facts” from the Embryo Project Encyclopedia:
- The rare condition diprosopus is also known as craniofacial duplication.
- Diprosopus refers to a baby born with a single torso, normal limbs and facial features, which are duplicated to a degree.
- In mild instances the baby may have a duplicated nose and the eyes may be spaced far apart. But in extreme cases the entire face can be replicated, hence the name diprosopus - Greek for two-faced.
- Most babies born with diprosopus are stillborn, and there are fewer than 50 cases documented since 1864.
- Where a baby is born with two complete identical faces, the condition is considered a rare variant of conjoined twinning.
- But while conjoined twinning is the result of an incomplete separation of two embryos, diprosopus is caused by abnormal activity of the protein Sonic Hedgehog (SHH).
- The protein is responsible for signalling craniofacial patterning during embryonic development, and among other things governs the width of facial features.
- Where the protein is found in excess, a baby will have wider facial features, and in extreme cases it can cause the duplication of those features.
- Diprosopus can be detected via ultrasound in pregnancy, or via CT scanning.
- One of the first indications of the condition is the detection of abnormally high amount of amniotic fluid present within the amniotic sac.
- There is currently no treatment to cure the condition and because of its rarity few treatment options or corrective surgery techniques exist.
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- Blue: Text by me; © Theo Todman, 2020
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