Preface: This article provides background information to the Multiverse of Minds hypothesis. If you'd like additional sources to be reviewed, please comment. I'll try to take a look at them, but it might need some time.

Motivation and Scope

Considering oneself fictionkin, e.g. being member of the dragon species which has been reported by cultures all over the world, but was never actually proven to have existed, calls for an explanation model other than the concept of reincarnation. One such model is provided by the so-called „multiverse hypothesis“, which is commonly adopted by fictionkin. It is also one amongst many theories in physics which aim to explain effects of classical mechanics, relativity and quantum mechanics, as well as observations made by physical cosmology. This blog entry will summarize and assess basic and also non-scientific online literature about the multiverse hypothesis as related to otherkin, but eventually also physical cosmology. In addition, related concepts, like e.g. the anthropic principle, are covered.

The multiverse in physics and philosophy

Wikipedia (publisher): „Multiverse“, Online, accessed 14.01.2019

This Wikipedia article is a summary of the multiverse hypothesis as discussed by physical cosmology. The term „multiverse“ is defined as „hypothetical group of multiple universes including the universe in which we live“, which in total would comprise everything that „exists“. The hypothesis was first proposed by Erwin Schrödinger in 1952. It is stated that prominent physicists are of divided opinion about the hypothesis; the main critisizm is that the theory can not be tested, which disqualifies it as a scientific hypothesis and puts it in the realm of philosophy. However, there are also prominent proponents of the hypothesis including Stephen Hawking (see below).

Furthermore, the article explains a classification related to multiverses as proposed by cosmologist Max Tegmark which comprises four levels. Level I states that the multiverse is comprised of an infinite number of so-called Hubble volumes, all having the same physical laws and constants, but otherwise different configurations. Level II foresees the existence of sub-universes with different physical constants. Level III relates to a mainstream interpretation of quantum mechanics by Hugh Everett, where each possible observation made from a quantum mechanical system corresponds to a different universe. Level IV is a mathematical interpretation: it considers all universes to be equally real and describable by different mathematical structures.

Another classification covered by the article is discussed by Brian Greene, who basically describes multiverse models which relate to other physical theories, including the Level 3 multiverse, or the string theory.

University of Cambridge (publisher): „Taming the multiverse—Stephen Hawking's final theory about the big bang“, Online, accessed 14.01.2019

This article contains a short summary of the last scientific paper of the late Stephen Hawking and Thomas Hertog about inflation of the physically observable universe. The article states that the results would, if confirmed by further work, indicate the existence of a non-infinite multiverse, which basically makes the multiverse theory more predictive and testable. Hertog believes that gravitational waves are a possible means for testing the theory.

Wikipedia (publisher): “Anthropic principle”. Online, accessed 14.01.2019

The Antrophic principle s a philosophical consideration which generally states that the observable universe must provide all requirements needed to host the life of the observer, and that this is the reason as to why the physical conditions within the universe are happening to be just right for supporting life. The term was introduced in 1973 by cosmologist Brandon Carter, and has been subject to controversial discussion since. It has especially been critizised that the principle wouldn't be falsifiable, thus be a non-scientific concept, and also that weaker formulations of the principle are truisms (statements that prove true by their formulation alone, e.g. “one is equal to one”). Today, there are multiple interpretations of the principle which can be classified into weak and strong interpretations. Weak interpretations generally use the principle as argument why nature has fine-tuned all physical constants exactly such as to support life in the universe. Strong interpretations go one step further and postulate that the existence of the universe itself is reasoned by conscious life as its purpose. One strong interpretation was formulated by John Archibald Wheeler and is called “participatory anthropic principle” (PAP). The PAP postulates that observers are essentially necessary in order to create the universe, and that only universes with conscious observers can exist. This strongly relates to quantum mechanics, where conscious observation (obtained by a measurement carried out by a living observer) itself changes the behaviour of quantum particles or waves. This leads to the postulation that the universe can only become “real” by the observation itself. In other words, the universe would collapse without a living conscious observer. This interpretation is controversially discussed. The principle has been connected to the multiverse hypothesis and string theory. It is especially conceived that the PAP could significantly reduce the number of possible universes in the multiverse, because only universes which could host a conscious observer could exist. The limitation of the set of universes again puts multiverse hypothesis on a firmer scientifical ground (cp. above: Taming the multiverse - Stephen Hawking's final theory about the big bang, 2018).

Wikipedia (publisher): “Introduction to M-theory”. Online, accessed 14.01.2019;
Wikipedia (publisher): “M-theory”. Online, accessed 21.02.2019;
C. Moskowitz: "String Theory May Create Far Fewer Universes Than Thought", Online, accessed 21.02.2019

The string theory is a mathematical model in theoretical physics which introduces hypothetical building blocks for our universe which only have one dimension (length), the so-called "strings". Hence it extends the classical particle physics, which works with zero-dimensional building blocks (point particles). According to string theory, strings are vibrating and interacting with each other within a universe with 10 dimensions, only four of which could be detected by human observers (length, width, height and time). Any observables in our universe, like matter, light or gravity, are a result of vibration of the strings within the 10 dimensions.

String theory came up in the 1980's; but with time, five versions of it were formulated which first seemed contradictory. Later it was discovered that the versions would relate to each other and could be transformed into each other. In 1995, theoretical physicist Edward Witten made a surprising proposal by stating that the five different string theories could be unified by assuming that strings are one-dimensional slices of two-dimensional membranes which vibrate within an 11-dimensional universe. This theory is called "M-theory", but is so far incomplete and not experimentally verified. M-theory is a candidate for provision of a great unified theory of theoretical physics which explains all fundamental forces of the universe as we know it, essentially combining the general theory of relativity and quantum mechanics.

String theory predicts the existence of some 10^500 versions of spacetime, making up a huge multiverse. The versions come up as different solutions to string theory equations. Many physicists are put off by the idea of such a high number of universes because literally everything is possible, which makes it hard to explain the existence of our specific universe. Still, others accept the possibility that emergence of our specific universe is just a random effect. Recently (2018) it has been discussed that some of the versions could be mathematically inconsistent or wrong.

Application of multiverse hypothesis to fictionkin

Infinitedraconity: „Soul of a Dragon“, Tumblr, Online, original post dated 25.04.2016, accessed 14.01.2019

This tumblr post is an answer to the question about how „does one think that they were a fictional character in a past life“. The answer proposes a multiverse with an infinite number of alternate universes and argues that, by the infinite nature, there must be at least one universe where a specific fictional plot would happen. This basically relates to the classic multiverse hypothesis as known from theoretical physical cosmology, adapted to the existence of fictionkin. The described multiverse is a Level III multiverse according to Tegmark's classification. However, the post does not relate the alternate fictional universe to our known physically observable universe or earth. The posting mentions the concept of „souls“, but fails to provide an explanation model as to how exactly fictionkin would appear on earth.

Micheleknight (publisher): „Your Quantum Soul. Just Where Are You in the Multiverse?“, Online, accessed 21.02.2019

Michio Kaku is a popular theoretical physicist who has been working on string theory and is known for his popular scientific presentations and media presence. The article named above suggests that Kaku has made a thought experiment in which he assumes that the soul is not hosted within the human body, but somewhere else. He suggests that our souls are multidimensional entities which could transit between parallel universes; however, no statement is made as to how the souls manifest within these universes.

Isonder: „Substitute To The Multiverse Theory“, Online, originally dated 28.03.2018, accessed 14.01.2019
This document aims at finding a substitute to the multiverse theory as used in the fictionkin community because it is „too flawed an argument to really keep“ and „not backed up by much scientific evidence“. The proposed substitute assumes that „souls“, obviously including fictionkin souls, would travel through the physically observable universe adhering to the laws of general relativity, i.e. not faster than light speed.

The work accordingly estimates the size of the observable physical universe, taking the expansion of this universe into account. Furthermore, the number of habitable planets in this universe as well as the number of life forms on these planets is estimated. It is assumed that 0.001% of the souls of life forms having died would travel to another planet 'to make an otherkin'. Finally, the number of otherkin humans on earth emerging by this model is estimated to 10.000 – 50.000. However, the likeliness that a specific fictionkin (e.g. Naruto) would emerge by this mechanism is still conceived very low.

This theory has a few drawbacks. First of all, it omits the classical multiverse theory by the statement that it is „flawed“ and „not backed up by much scientific evidence“. This is generally true, but by no means a valid reason to completely omit the theory as a working thesis - unless an alternative working thesis is found which is better suited to explain physically observable phenomena. This does not seem to be the case for the proposed substitution, as is stated by the autor himself. Second, the assumption of „souls“ traversing through space at maximum light speed is also not backed up by any scientifical evidence; hence, the proposed substitute does not seem to provide a model which has more scientifical backup than the original theory. Third, the calculation fails to realize that modern quantum physics indicates that information can be transmitted instantaneously by quantum teleportation. There is no evidence that the transmission of „soul“ information would need a physical communication channel. If it would base on quantum teleportation, then the limitation set by the speed of light would be obsolete. Hence, the result as calculated by Isonder can only be considered a lower estimate. Last but not least, the assumption that a „soul“ would be an entity bound by the currently known laws of physics seems quite a strict conceptual limitation, and again is not backed up by evidence. It would actually seem more intuitive to assume that „souls“ are not generally limited by known physical rules, since physics fails to explain their existence in the first place.