© Author(s) (or their employer(s)) 2022. Reuse permitted under CC BYNC. No commercial reuse. See rights and permissions. Published by BMJ. InTroduCTIon Although the content of one’s consciousness changes through time (eg, personality changes), their identity or psychological continuity still, somehow, remains the same. In fact, typical human selfcontinuity—the unity of consciousness over time—spreads out over a period of hours, from one episode of dreamless sleep to a waking state. I wake up, eat breakfast, take a shower, get dressed, go to the institute and start the routine work of my scientific life. I am conscious the whole time, and the experiences I have at each phase of my morning, belong to a single stream of consciousness. However, this smooth subjective occurrence of self does not function for some people. In some patients, like those with schizophrenia, selfcontinuity abruptly ceases. They experience a kind of divorce from reality with various behavioural disturbances such as hallucinations, delusions and catatonia. In practice, the patient experiences a weird sense of losing their identity. It seems that they are unable to preserve their identify of self with the outside world. In other words, they lose contact with the reality of the world. There is also a large body of literature suggesting that those with schizophrenia turn away from the outside world and become concerned with their own subjective state. By a closer look at some of the thought disorders of schizophrenia, we notice that a metaphoric glue in the stream of consciousness is missing. This includes derailment or tangentiality or knight’s move thinking—a failure to follow the social norms of conversation and not sticking to the overall theme of the discussion, or pressure of speech— a speeding up of the flow of speech. Besides, there is evidence indicating that their perception of the world differs qualitatively from that of a normal individual; this, in consequence, leads to a deprivation in their gratitude towards the outside world. This is exactly the point which we should notice more. Why do they lose contact with the outside world? What happens inside the minds of these individuals that makes them disconnected? Is it just neurodegeneration in a region of the brain (such as in Alzheimer’s) or lack of a special kind of neurotransmitter (such as in Parkinson’s disease)? Or, is it only a genetic problem? Although many research institutions that investigate the aetiology of schizophrenia have concentrated on organic deficits, they are unable to reach a consensus on why these people lose their thread of self. Before answering these questions, one of the main locomotion theories after the dawn of the cognitive revolution in the mid20th century—the reafference principle (von Holst and Mittelstaedt)—should be reviewed. One may presume that the answer to these questions lies within a better understanding of this theory.

Lockean views of personal identity maintain that we are essentially persons who persist diachronically by virtue of being psychologically continuous with our former selves. In this article, I present a novel objection to this variant of psychological accounts, which is based on neurophysiological characteristics of the brain. While the mental states that constitute said psychological continuity reside in the cerebral hemispheres, so that for the former to persist only the upper brain must remain intact, being conscious additionally requires that a structure originating in the brainstem-the ascending reticular activating system-be functional. Hence, there can be situations in which even small brainstem lesions render individuals irreversibly comatose and thus forever preclude access to their mental states, while the neural correlates of the states themselves are retained. In these situations, Lockeans are forced to regard as fulfilled their criterion of diachronic persistence since psychological continuity, as they construe it, is not disrupted. Deeming an entity that is never again going to have any mental experiences to be a person, however, is an untenable position for a psychological account to adopt. In their current form, Lockean views of personal identity are therefore incompatible with human neurophysiology.

which consciousness seems to be absent, including dreamless sleep or coma. There are also a variety of circumstances that can change the relationship between Consciousness is being aware of something internal to one's self, or of states or objects in one's external environment. It has been the topic of extensive explanations, analyses, and debate among philosophers, scientists, and theologians for millennia. There is no consensus on what exactly needs to be studied, or whether consciousness can be considered a scientific concept. In some explanations i An unsolved problem in the philosophy of consciousness is how it relates to the nature of personal identity. This includes questions regarding whether someone is the "same person" from moment to moment. If that is the case, another question is what exactly the "identity carrier" is that makes a conscious being "the same" being from one moment to the next. The problem of determining personal identity also includes questions such as Benj Hellie's vertiginous question, which can be summarized as "Why am I me and not someone else?". The philosophical problems regarding the nature of personal identity have been extensively discussed by Thomas Nagel in his book The View from Nowhere. A common view of personal identity is that an individual has a continuous identity that persists from moment to moment, with an individual having a continuous identity consisting of a line segment stretching across time from birth to death. In the case of an afterlife as described in Abrahamic religions, one's personal identity is believed to stretch infinitely into the future, forming a ray or line. This notion of identity is similar to the form of dualism advocated by René Descartes. However, some philosophers argue that this common notion of personal identity is unfounded. Daniel Kolak has argued extensively against it in his book I am You. Kolak refers to the aforementioned notion of personal identity being linear as "Closed individualism". Another view of personal identity according to Kolak is "empty individualism", in which one's personal identity only exists for a single moment of time. However, Kolak advocates for a view of personal identity called "open individualism", in which all consciousness is in reality a single being and individual personal identity in reality does not exist at all. Another philosopher who has contested the notion of personal identity is Derek Parfit. In his book Reasons and Persons, he describes a thought experiment known as the teletransportation paradox. In Buddhist philosophy, the concept of anattā refers to the idea that the self is an illusion. Other philosophers have argued that Hellie's vertiginous question has a number of philosophical… There are…