The introduction of the problem of personal identity in the university course of philosophy

The article considers the introduction of the problem of personal identity in the structure of the course of philosophy. The introduction of new material is the attempt to redesign the academic course of philosophy, simultaneously keeping its traditional structure. The problem of personal identity is a topical issue in analytic philosophy. However, it is not much learnt in Ukraine, where academic circles mostly orient to continental philosophy. The paper analyses the subject area of personal identity: its metaphysical status, the nature and conditions of personhood, the possible criteria, and the method of though-experiment. Then, it shows the steps of introducing personal identity in the course of philosophy. The novelty of the article is in the fact that the problem of personal identity is introduced for non-philosophy students for the first time at Ukrainian university course of philosophy.


Introduction
The problem of teaching philosophy at university is always one of the most topical among Ukrainian educators. For philosophy is a compulsory course for all students of the bachelor's programme, it is taught in all higher educational institutions in Ukraine. At Kryvyi Rih State Pedagogical University, philosophy is a compulsory course for non-philosophy students, who are in the second year of the bachelor's programme. Under the concept of nonphilosophy student, we understand students who do not major in philosophy. For Kryvyi Rih State Pedagogical University prepares future teachers, but not professional philosophers, all students belong to this category. Philosophy plays an essential part in the formation of worldview, and therefore, great attention should be paid to it. The course of philosophy is taught for two academic terms. It includes two thematic parts. The first one outlines the history of philosophy from Ancient Indian, Ancient Chinese, and Ancient Greek philosophy to analytic philosophy of the twentieth century. The second part concerns the main problems of philosophy and its branches: metaphysics, theory of knowledge, philosophy of mind, philosophy of history, value theory, philosophical anthropology, etc. In the third year, the students can choose two other elective courses out of the following: aesthetics, ethics, cultural studies, religious studies, social and political philosophy, and logic. The master's degree students study one of these courses: critical thinking, philosophy of education, and philosophy of science. The choice of courses depends on the programme. For example, students, majoring in chemistry or biology, study philosophy of science, psychology students and education majors study the philosophy of education. PhD students also study the advanced course of * e-mail: olifer.olena@kdpu.edu.ua philosophy and the course called methodology and organization of scientific research.
For the course of philosophy is taught to all students of the bachelor's programmes in Ukraine, the problems of methodology and syllabus improvement are the most discussed at the departments of philosophy all over Ukraine. I. Bychko outlines the necessity to reconsider the syllabi of the course of philosophy taught at Ukrainian universities. He admits that some concepts and theories have not been reconsidered and updated since 1938. The author suggests excluding the following aspects from the syllabi: the themes concerning so-called "the basic question of philosophy" introduced by F. Engels; the way to present the history of philosophy through the opposition of materialism and idealism; the dialectical method as the main one, considering society, a person and nature. I. Bychko admits that the understanding of social problems and personhood should be reconsidered [1]. It is also essential to add new themes and problems to the course of philosophy.
T. Yashchuk notes that educators should bring innovation into the course of philosophy. The innovative course of philosophy should be based predominantly on modern philosophical discussions. It should include such systems as analytic philosophy, phenomenology, poststructuralism, post-Marxism, and others [2].
V. Ryzhko thinks the teachers should reconsider the structure of a modern course of philosophy. Firstly, it is necessary to introduce the theoretical part, including historical aspects and a description of the main philosophical categories. Then, the second part of the course should be devoted to the reading of the original philosophical texts and their discussion at the seminars [3].
In his papers [4,5], I. Karivets shows the importance to design the course of philosophy, so that it develops re-flective thinking. According to the author, philosophical thinking comprises three stages: speculation, abstraction, and theory [5, p. 83]. A student, who gets through all these stages, starts perceiving the world as the complicated unity of interconnected processes and gains a fundamental theoretical worldview essential for the future professional life.
In their papers [6,7], M. Maksiuta and O. Onyshchuk, outline the idea of the reconsideration of methods in philosophy teaching. O. Onyshchuk writes that the course of philosophy must be considered as propaedeutics to any field of knowledge. Therefore, students must not only learn the material but also develop their own beliefs in the truth of certain conclusions that must be elements of their spiritual world [7, p. 140]. This purpose can be achieved if the philosophy teaching meets these requirements: understanding the process of learning as a cognitive process aimed at the development of critical thinking and creativity; considering learning as the comparison of new information with already known; creating a psychologically comfortable environment; organizing the educational process as the acquisition of personal experience; taking into account the uniqueness of each student [7, p. 140]. K. Kyrylenko states that the peculiarity of philosophy is its systemic nature. It is possible to unite different themes in a single philosophical course, using the methods of active learning (projects, discussion, creative tasks, essay writing) [8].
Thus, the mentioned philosophers and educators show that the syllabus of the course of philosophy needs constant improvement. The focus should be on contemporary discussions and categories.
The introduction of the new material causes some methodological questions. That is the question about the content of new information, i.e. which information should be added and how to choose this new material. In Ukrainian universities, there is a strong tendency to introduce new philosophical discussions from continental philosophy.
But at Kryvyi Rih State Pedagogical University, the Department of Philosophy develops a philosophic approach based on analytic philosophy. Therefore, the material of the course should also be topical for contemporary debates in analytic philosophy, interesting for the students and connected with other topics in the course.
These criteria of the theme choice cause one more problem: the problem of its placement within the course. The course of philosophy presupposes the structure when the first part is devoted to the historical development of philosophy and the second one comprises metaphysics, philosophy of mind, theory of knowledge, philosophy of science, social philosophy, philosophy of history, value theory, and philosophical anthropology. The structure is traditional developed and being practiced for many years so it is difficult to redesign the course completely. Moreover, it presupposes 34 hours of lectures and 34 hours of seminars. The limitation of in-class hours does not allow either devoting a separate seminar to certain new debates or introducing much new material, as it will be information overload. Thus, the new material should be introduced within the existing structure. That raises a question about the method of the material introduction. After consideration, we have chosen the problem of personal identity to be introduced in the structure of philosophy course.

Personal identity in socio-cultural discourse
Who am I? What is meant to be a person? Does the word "I" refer to a body or a soul? How am I different from other people? While studying philosophy students may ponder over these questions. The professional philosophers would emphasize that these questions belong to the identity problem.
The notion of personal identity is in the focus of sociocultural discourse. S. Hall admits that there has been "a veritable discursive explosion in recent years around the concept of identity" [9, p. 1]. E. Erikson notes that the concept of identity is so widely used that it seems to be understandable for everyone without any definitions [10, p. 15].
There are different approaches to personal identity in socio-cultural discourse. Psychologists consider it within the paradigm of self-concept and the formation of the self via socialization. W. James was the first who introduced this viewpoint. He considers that the self-concept of a person appears as the unity of distinguishes four constituents: the material self, the social self, the spiritual self, and the Pure Ego [11, p. 280]. The spiritual self and the Pure Ego are the concepts of the high level of abstraction. They are pure ability to think and the position from which a person deliberates. The material self consists of a body and property including clothes and houses. The social self means social recognition. W. James emphasizes that an individual can possess several social selves; the exact number of social selves equals the number of people, carrying an image of the individual in their consciousness [11, p. 280]. The people, who belong to one social group, share the same image of the individual. The number of social selves is the same as the number of social groups where the individual interacts.
C. H. Cooley introduces the theory of looking-glass self, in which he emphasizes that personhood is social in its nature. It emerges as a result of the interiorization of interaction with other people. The self as the unity of all social experiences contains three elements [12, p.  He distinguishes consciousness as the ability to be aware of emotional states and self-awareness as the fundamental property of the self when an individual considers himself or herself as an object. Self-awareness is also a product of society because the individual exists not only in a social group but also because he or she constitutes self from the experience of his influence on others. The self divides into two parts: "I" and "me". "I" arises from experience and is based on memory. It is the ability to be aware of oneself as a subject, to ascribe certain experiences and feelings. "I" is the reaction of a person to social norms. "Me" is based on self-awareness, on a reflective appeal to oneself. These two components of the self do not oppose each other, and they do not reduce to each other. Their mutual dialectical influence results in the creation of personal identity as the unity of the self [13].
S. Stryker and P. Burke describe identity as the hierarchical entity of social roles [14,15]. P. Burke distinguishes the following types of its components: (1) role-based identities, (2) group identities, (3) personal identities. According to this hierarchy of identities, self-verification and selfassessment take place [15, p. 112]. He pays special attention to personal identity which is the embodiment of culturally recognized traits, expectations of the individual.
According to H. Tajfel, identity may be defined as "the individual's self-definition in a social context" [16, p. 68]. Social identity is the result of a long process that includes several stages: (1) social categorization, i.e. the analysis of the environment and the selection of essential social groups from the social space; (2) social identification, which is associated with the identification of the individual with the selected group; (3) social identity (a result of identification), which manifests in stable notions of belonging to a particular social group [16,17]. Social identity is a cognitive construction, and it includes knowledge of social group membership, attitudes towards that group, and emotional significance about that membership [17, p. 15].
Therefore, in socio-cultural discourse the notion of personal identity is understood as the formation of the self and the attribution of social roles or self-definition to a social group.

The problem of personal identity in philosophy
According to the historical studies conducted by R. Martin and J. Barresi, the problem of personal identity goes back to Ancient Greek philosophy, as it was introduced by Plato and Aristotle as a part of their philosophical systems [18, p. 1]. R. Martin and J. Barresi, U. Thiel, and K. J. Seberger-Forstrom consider the historical aspects of the personal identity problem [18][19][20]. In papers [21][22][23], we have outlined the main periods of the personal identity problem. In this article, we present the key points of our study.
Although the personal identity problem has been developing since the classical period of Ancient Greek philosophy, it was regarded implicitly as a part of the other problems till Early Modern philosophy. Aristotle and Plato considered it in the context of the relation between a soul and a body. In the Middle Ages, the personal identity problem was interpreted as the principle of individuation: a person remains the same as the unity of the same soul in one body.
T. Hobbes is one of the first in the Early Modern philosophy, who explicitly formulates the problem of personal identity. He outlines this notion in his wellknown paradox about the ship of Theseus. However, the analyses it in Aristotelian terms of matter and form, adding the scholastic principle of individuation [24]. For R. Descartes, personal identity is cogito. A person remains self-identical because he or she continues thinking. For thinking is an attribute of immaterial substance, the problem of personal identity can be understood as the problem of the same immaterial substance. This view is close to the medieval notion of the sameness of person as the unity of the body and the soul. So Descartes does not pioneer in the development of personal identity problem [25].
However, Cartesian philosophy concerning the self, innate ideas, and mind-body dualism makes J. Locke develop his empirical theory of knowledge, where the problem of personal identity arises explicitly in a new perspective as an essential part of epistemology and metaphysics. In Chapter 27 of "An Essay Concerning Human Understanding", J. Locke grounds unsubstantial theory of personal identity. The philosopher distinguishes three sorts of substances: God, finite intelligences (spirits or angels) and bodies [26, p. 183]. The last category includes things (a mass of matter), plants, animals and a person. Plants and animals keep their identity if they continue their life, and their organism consists of the same parts.
Then, J. Locke states that a man and a person are two different ideas; they have different principle of identity. A man is a continued life in "a living organized body" [26, p. 187]. The principle of identity of a man is the same as for an animal or a plant. However, he defines a person as "a thinking intelligent living that has a reason and reflection, and can consider itself as itself, the same thinking thing in different times and places; which it does only by that consciousness which is inseparable from thinking and, as it seems to me, essential to it: it being impossible for anyone to perceive without perceiving that he does perceive" [26, p. 188]. A person is also "a forensic term appropriating actions and their merits, and so belongs only to intelligent agents capable of a law, and happiness and misery" [26, p. 198]. It means a person is not a substance, but an agent, the subject of an action and thoughts. An agent can perceive, ascribe actions and thoughts, and remember them. An agent is accountable for ascribed actions. If a person can do that, he or she is conscious. Thus, consciousness becomes the criterion of personal identity. The philosopher emphasizes: "Nothing but consciousness can unite remote existence into the same person" [26, p. 196]. The substance, material or immaterial, is not able to do that. J. Locke's theory of personal identity influenced the development of philosophical thought in Early Modern philosophy. After J. Locke's book, G. W. Leibniz, J. Butler, T. Reid, D. Hume, and I. Kant analysed this problem in their philosophical treatises.
G. W. Leibniz develops an ethical view on personal identity. He states that a person is not just a rational creature, but a subject of moral responsibility [27]. T. Reid distinguishes identity in general and personal identity as two different categories. He defines identity in general as "a relation between a thing which is known to exist at one time, and a thing which is known to have existed at another time" [28, p. 201]. This definition implies the idea of persistence over time or, as he puts it, "an uninterrupted continuance of existence" [28, p. 201]. Personal identity supposes the idea of persistence of a person over time and the notion of this uninterrupted existence reflected in the consciousness of this person. Thomas Reid emphasizes that personal identity is "the continued existence of that indivisible thing which I call myself" [28, p. 203]. That means personal identity is the question of the continuation of the self over time. In other words, the category of personal identity explains why a person who existed yesterday is the same as that person, existing today, and why today's person will be the same as tomorrow's one. J. Butler and T. Reid introduce essential critical remarks on the personal identity problem, for example, the problem of circularity of consciousness, which is one of the prominent topics in analytic philosophy, especially for S. Shoemaker and P. Grice. D. Hume describes eliminative approach to the self, saying that the self is not a single unity or a structure, but "the bundle or collection of different perceptions" [29, p. 165]. The contemporary philosopher D. Parfit uses Hume's conception of the self as one of the sources of for his non-reductionism.
I. Kant considers personal identity ethics. The philosopher views a person as a moral agent, a source of responsibility and obligations [30]. Kantian philosophy affects considerably the contemporary discussion of the problem of personal identity: C. Korgaard's monographs and articles are an example of a neo-Kantian theory of personal identity [31][32][33]. After I. Kant, the interest in the problem of personal identity slightly decreased.
In the 20th century, the problem has returned in the focus of philosophical discussion in analytic philosophy. In 1941, P. Grice introduced the neo-Lockean theory of personal identity [34]. After that, neo-Lockean approach was developed by S. Shoemaker, B. Williams, E. Olson and others [35][36][37].
How do philosophers formulate the problem of personal identity? E. Olson states it as the question of possible circumstances when a person existing at one time is identical with (or the same) as a person existing at another time? [44, p. 356]. E. W. Hall says that the personal identity problem presupposes the contradiction be-tween numerical and qualitative types of identity. Numerical identity is the sameness in number, and qualitative identity is the sameness of properties. The contradiction appears when, for example, a person experiences some changes in character or behaviour [45, p. 88]. This person remains the same in number, but habits, tastes, thought, ideas, manners are completely different, and so we can say that a person isn't the same. Thus, E. W. Hall tries to analyze what makes a person the same or identical over time: the same body or the same behaviour and experience. H. Frankfurt considers personal identity as the problem of the nature of a person and the conditions of personhood [40, p. 113]. That means every person shall be identical over time and identity is an essential feature, so there is no person without personal identity. For C. Korsgaard, C. Rovane, and M. Schechtman, personal identity is the matter of personal identity is the process of constant re-identification of a person in narrative or interaction with other people [31-33, 41, 42].

The aim and the objectives of the study
The paper aims to show the problem of personal identity in the structure of the course of philosophy as its important part. The article has the following objectives: (1) to analyse the subject area of the problem of personal identity,

The metaphysical status of personal identity
The metaphysical status of personal identity considers two possibilities of interpretation of the mentioned concept. In Early Modern philosophy and contemporary neo-Lockeanism, personal identity is considered as the relation between person-stages. J. Butler emphasizes that the identity ascribed to a person existing over time is the same relation that exists between two things. He states that personal identity should be understood "in a strict and philosophical" sense, i.e. the identity of a person is the same category as logical identity [46, p. 319]. This category is symmetrical, transitive, and reflexive. Thus, if two stages of the person's being are symmetrical and characterized by reflexivity and transitivity, a person possesses self-identity. D. Parfit admits that identity as a formal category is the relation one-one and it does not have degrees: if it allows degrees, the relation between is not identity, but similarity. The author emphasizes: "Identity is all-or-nothing" [47, p. 11]. However, reflexivity and transitivity between two episodes in the life of a person can fail. T. Reid showed that in his famous thought-experiment about a boy, an officer and a general. Imagine a boy who robbed an orchard at school and who was flogged for that. Then, he becomes an officer and, being in the decisive battle, he takes the standard of the enemy. In the battle, he remembers that situation at school. After that, he becomes a general who remembers being an officer in the battle, but he completely forgets the episode when he was flogged at school for robbing an orchard. T. Reid concludes that the officer identifies himself with that schoolboy, but the general does not. The philosopher considers the following: "He who was flogged at school is the same person who took the standard, and that he who took the standard is the same person who was made a general [...] But the general's consciousness does not reach so far back as his flogging, therefore, according to Mr. Locke's doctrine, he is not the person who was flogged. Therefore the general is, and at the same time is not, the same person with him who was flogged at school" [28, p. 214]. Thus, the boy and the officer are two identical person-stages, as well as the officer and the general. However, there is no identity between the personstages of the boy and the general.
B. Williams shows some contradictions, when we think of personal identity over time in his famous thoughtexperiment about Charles, Robert, and Guy Fawkes [36]. Imagine that a young man called Charles undergoes a change of character and memories, so his original personality vanishes. He starts believing that he is Guy Fawkes, a participant of the Gunpowder Plot in 1605. Charles has got the same memory, manners, and behavioural patterns as Guy Fawkes. Is it possible for two people, Charles and Guy Fawkes, to be the same person? If we assume that Charles is identical to Guy Fawkes, the thoughtexperiment goes to the second stage. Another person, called Robert, undergoes the same procedure of character change, so he also receives the personality of Guy Fawkes. Thus, Charles and Robert identify themselves with Guy Fawkes. Are three of them the same person? Is Charles the same person as Robert? If we assume that endurance of memories and knowledge and the extension of the same consciousness over time make a person self-identical, then we can also assume that Charles and Robert are the same persons as Guy Fawkes. However, Charles and Robert are simultaneously at different places and receive different experience. Thus, transitivity between them disappears, so they are not identical but similar to each other [36, pp. 4-11].
M. Schechtman notes that personal identity is considered as the duration of consciousness over time, but con-sciousness cannot be analyzed in term of formal logic. Suppose, there is a patient with Alzheimer's disease, who often forgets the past, but then remembers again. If personal identity is analyzed as a relation between person-stages, such a patient would constantly lose and restore personal identity. And if the possession of personal identity is the ground of personhood, a patient with Alzheimer's disease can be regarded as a person at one time and as a non-person at another time, but that is impossible [42, p. 91]. M. Schechtman concludes that personal identity is not a relation between person-stages over time, but a characteristic of the united self [42, pp. 167-168].
In the narrative and normative approaches to the problem of personal identity, the philosophers develop the idea of the person constitution. A person is considered as an active being who realizes activity on practice. As a result, a person gets different experiences and has to unite them in a single entity to reduce inner conflict between motives. In such a way, the self emerges. While the self exists as the unity of experience, it stays numerically unchanged. Thus, personal identity is the characteristic of the self as a unity of experience when a person constitutes personhood in the process of life.
The philosophers explain the emergence and the duration of personal identity in different ways. For example, C. Rovane considers personal identity as the result of being in agency-regarding relations -interpersonal communication and interaction [41, p. 49]. For C. Korsgaard, personal identity emerges in the process of deliberation and the ascription of actions [32]. For H. Frankfurt, volition results in personal identity, and for M. Bratman, personal identity constitutes itself in the process of planning [40,48].

The nature and conditions of personhood
What is meant to be a person? Is a person a substance? What is the difference between persons and non-persons? Is it possible to be a person without personal identity? R. Descartes and G. W. Leibnitz identified the origin of the self, and personhood with the substance. J. Locke introduces a new definition of a person, according to which, a person is characterized by self-knowledge and accountability of own actions. The existence of personhood extends over time back to the beginning of self-knowledge, which reflects in memory. This unsubstantial approach to the understanding of personhood and the self is developed in contemporary discussion.
J. Mackie interprets a person as a unity backwardslooking memory and forward-looking concern which emerges as the result of action ascription [49, p. 177]. C. Rovane defines a person as an agent with the firstperson perspective -the ability to ascribe "I", understanding actions as own. Such agent achieves the rational unity, i.e. the unity of the self in mutual relations with other agents [41, pp. 209-210]. G. Strawson considers a person as the unity of three fields: the field of responsibility, the field of consciousness, and the field of concernment. The author emphasizes that a person is both a subject of experience and a moral agent since a person takes responsibility for actions [50, pp. 24-25]. C. Korsgaard considers that a person's nature from the teleological viewpoint. A human being is a person if he or she achieves the purpose of personhood and realizes his or her functions as a person. The philosopher states that such function is the selfmaintaining activity, i.e. maintaining the unity of self [32, p. 141]. Thus, the mentioned authors interpret the nature of personhood from the viewpoint of action appropriation, which results in the achievement of the unified self. When a human being acquires the unified self, he or she becomes a person, capable of self-knowledge. Personal identity emerges simultaneously with the unified self. And while a person keeps this continuity of the self over time, personal identity exists over time. Therefore, personal identity is a category for distinguishing persons from non-persons. A person is an agent with personal identity.
However, E. Olson notes, a person is "a functional animal, that is a person is just a stage in the life of a human being or, as he puts it, a human animal. Personhood is not a necessary condition for a human being to exist" [37, p. 109]. Firstly, a human being is an animal of a certain biological organization, and then, it becomes a person. The person-stage does not coincide in time with the human life: a fetus and a baby do not have either self-knowledge or unified self; therefore, they are not treated as persons; the person-stage may be suddenly interrupted when a human being is in a coma or the vegetative state. Thus, E. Olson concludes that the philosophers should consider personal identity as the biological continuity of life [37, p. 16].

The criteria of identity
The problem of the criteria of personal identity is the question of sufficient conditions, when a person is considered identical at one period of time to a person, existing at another time. The viewpoint that personal identity can reduce to a criterion or criteria is known as reductionism. The opposite point of view is non-reductionism. In publications and monographs [38,39,[51][52][53][54], the authors distinguish two criteria: psychological and physical. The philosophers describe these two criteria in their variations.
According to B. Garrett's definition of the psychological criterion, personal identity over time "consists in the holding of the relation of psychological continuity between a person at different times" [53, p. 41]. The psychological criterion exists in the following variants: (1) as continuity of memories, (2) as continuity of consciousness, (3) as mental connectedness.
In Early Modern philosophy, personal identity is viewed as the continuity of memories. In analytic philosophy, P. Grice and S. Shoemaker consider identity as continuity of consciousness, adding other mental faculties to memories [34,35]. They think that personal identity is a formal relation between two stages. H. Noonan and R. Nozick consider identity mental connectedness, but they admit that identity between person-stages is not a strict one-one relation, and it can have degrees of similarity [38,39].
There are some critical remarks to the psychological criterion. Memory continuity interrupts when a person forgets some important episodes or suffers from amnesia. Memory is circular: if a person has memories, it means a person has already achieved the unified self, so memory cannot presuppose personal identity. A person may have false or quasi-memories, when he or she remembers was a witness of action but remembers it as his or her own. Consciousness interrupts when a person is asleep or in a coma. It is complicated to analyze consciousness as the criterion of identity if the later is regarded as a formal logic relation.
In the publications [36,[51][52][53], the physical criterion is defined as the spatial and temporal continuity of a person's body (or a body part). All mental activities and consciousness are considered as the properties of matter. The physical criterion exists in several variations. B. Williams identifies a person with a body, as the existence of a body is a pre-condition of the existence of consciousness [36]. R. Sperry, J. Shaffer and T. Nagel consider the unity of consciousness as the feature of brain activity [55][56][57]. So, while a brain continues to function, a person exists, even if the rest of the body does not survive. T. Nagel concludes: "I am identical with my brain" [57, p. 40]. E. Olson and P. Snowdon introduce animalism as a variant of the physical criterion [36,44,58]. According to P. Snowdon, a person is numerically identical to a human animal, so if this human animal keeps biological continuity, i.e. life, it can be a person [58, p. 172].
D. Parfit introduces non-reductionism [47,51]. According to the philosopher, a criterion of personal identity has to presuppose personal identity in all situations without exceptions. However, both known criteria accept expectations, which D. Parfit shows in his version of the fission problem -a thought-experiment considering personal identity. Originally, this thought-experiment was introduced by S. Shoemaker. However, D. Parfit reconsiders it. Suppose, there is a person, named Brown, whose brain was divided into two halves so that each half of the brain remained the same in its functions as the whole brain. Then, these two parts were transplanted into two different bodies, and the original body was destroyed. D. Parfit asks: what will happen to Brown after the transplantation of the brain parts into new bodies. The philosopher suggests three possible solutions to the problem: (1) Brown will die; (2) one of two persons will be Brown; (3) Brown will continue to exist simultaneously as two persons (Brown 1 and Brown 2 ) [47, p. 5].
The first option is quite questionable because one brain transplant is often successful, so double success can not lead to double failure when both parts of Brown's brain will stop functioning. If one part of the brain functions and the other does not, Brown will continue to live as Brown 1 or Brown 2 . Then, this person will be identical to Brown who existed before the operation. Thus, Brown will keep his identity over time. However, the problem arises as a result of double success if both parts of the brain function in two new bodies. In that case, Brown will be in two different places at once, and that is logically impossible. Moreover, Brown 1 and Brown 2 cannot maintain their identity with Brown because their content of consciousness at the same time will be different [47, p. 5].
D. Parfit illustrates that both identity criteria are questionable. The psychological criterion bases on qualitative identity, so, when Brown 1 and Brown 2 appear, the identity of consciousness turns into similarity. The numerical identity of the brain as a body part is violated in this thought-experiment: two persons identical persons cannot exist at the same time. Thus, the philosopher concludes that the category of identity is not necessary for describing a person's continuity over time.

Studying the problem of personal identity through the method of thought-experiment
Analyzing the problem of identity as a fundamental relation, the philosophers often use the method of thoughtexperiment. The most known example concerning identity is the thought-experiment about the ship of Theseus. This method is also widely used in the problem of personal identity. B. Garrett admits that the philosophers show their interest in thought-experiments in personal identity because "consideration of ordinary cases will not help us to decide the issue" [53, p. 14]. J. Locke introduces the mentioned method in the personal identity problem. In Chapter 27 of "An Essay Concerning Human Understanding", J. Locke considers such examples as the example of the cut finger, body change between a prince and a cobbler, turned into an animal Heliogabalus, and the Day-man and the Night-man in one body [26].
In our opinion, the best-described thought-experiment is the fission problem. S. Shoemaker, D. Parfit, R. Nozick, H. Noonan, and others consider its versions. The typical script of the fission problem describes the situation when a person's brain is divided into two parts or when a person is reduplicated. Instead of one person, two identical people appear. As shown in the previous section, the fission problem disputes the existing criteria of personal identity and is the verification tool for any possible criteria of identity.
The use of thought-experiments has both advantages and disadvantages. B. Garrett thinks that "thoughtexperiments can be useful in understanding the structure of a concept and the relative importance of its different strands, provided that there is general agreement about the best description of the thought-experiment" [53, p. 14]. K. Wilkes criticizes this method for fantastic scripts violating all possible physical laws, and therefore, the results are doubtful. In her opinion, it is necessary to use this method only in conditions close to reality [59]. Nevertheless, the significant numbers of thought-experiments illustrate that this method is very productive, and it should be used not only by philosophers but also by educators in teaching the problem of personal identity.

The steps of the introduction of the problem of personal identity in the course of philosophy
The first step towards introducing the problem of personal identity is to place it in the structure of the philosophy course. There are three possible variants for that. Firstly, for the problem of personal identity has a rich philosophical background, it may be introduced in the context of Early Modern philosophy. It gives one more necessary links between Cartesian and Lockean philosophy because one of J. Locke's reasons to introduce the problem of personal identity was to show weaknesses of Cartesian philosophy. It also helps to form a better understanding of the British Early Modern philosophy and its development from Thomas Hobbes to David Hume since all of them contributed to that problem and considered the notions of personhood, consciousness, and knowledge. Secondly, the problem of personal identity has connections with philosophical branches: metaphysics, theory of knowledge, and philosophy of mind. The analytic philosophers consider consciousness as a possible criterion of personal identity, and that gives connections to the mind-body problem. Personal identity also raises questions about the emergence of consciousness. The problems of continuity of memories, quasi-memories and the role of other mental faculties in the constitution of the self connect the concept of personal identity with philosophy of mind, and theory of knowledge. So, the problem of personal identity may be introduced at lectures and seminars concerning mentioned topics.
Thirdly, the problem of personal identity also outlines the difference between person and non-persons and concerns the notion of personhood, so it may be considered in philosophical anthropology.
For the problem of personal identity has a historical background and is connected with other philosophical branches, we decided to present it twice: (1) in the historical part in the lecture and the seminar devoted to Early Modern philosophy and (2) in the topic of philosophical anthropology. The first introduction of personal identity is in the topic "Early Modern Philosophy", which creates the necessary link between European (Cartesian) and British philosophy. The second introduction is in the theoretical part of the course, in the topic "Philosophical Anthropology" that is pre-last in the structure of the course. The problem of personal identity is presented in the context of nature and conditions of personhood, metaphysical status of personhood and the problem of definition of personhood. Placing this problem almost at the end of the course helps the students to summary students' knowledge from topic devoted to metaphysics, epistemology, and philosophy of mind. The next step is to provide the students with the reference list and necessary learning material. As mentioned, the problem of personal identity is not typical for continental philosophy, so it is not represented in the Ukrainian philosophic textbooks and companions. In spring 2021, the Department of Philosophy of Kryvyi Rih State Pedagogical University is going to publish the tutorial, where personal identity is analysed in the chapter "Philosophical Anthropology". The list of references includes several papers in the academic journal "Actual Problems of Mind" (the publisher is Kryvyi Rih State Pedagogical University). The articles describe the historical development of the problem in Ancient Greek and Early Modern philosophy and present three approaches to the problem: metaphysical, normative and narrative [21][22][23].
Each seminar typically consists of two parts: discussion of the problem questions concerning theoretical aspects of a topic and the analysis of primary sources. So they constitute the essential part of the reference list. For the seminar, devoted to Early Modern philosophy, the reference list includes the following sources: (1) J. Locke's "An Essay Concerning Human Understanding", (2) J. Butler's dissertation "Of Personal Identity", (3) T. Reid's "Essays on the Intellectual Powers of Man". Making the reference list on personal identity, one will face difficulty because many primary sources have not been translated into Ukrainian. The students do not speak English on the advanced level either to read and analyze philosophical texts in the original. Thus, one of the main tasks is to translate key chapter and papers on personal identity. We have published the translation of J. Butler's dissertation "Of Personal Identity" to help students to understand this problem better [60]. For we were the first in Ukraine in the translation of this material, this fact is considered as the novelty of our work. The further perspective is to publish the translation of T. Reid's chapters, concerning personal identity.
The third step is about methods of introduction of the personal identity problem in seminars. The main method to introduce this problem is through though-experiments. In the topic "Philosophy of Mind", students get familiar with that methodology and usually analyze such puzzlecases as "The Chinese room", "Mary's Room", "The Brain in a Vat". In the topic of philosophical anthropology, the students revise the learnt information and analyze personal identity through examples of thought-experiments, including B. William's scenario of Charles' and Robert's personality shifts and S. Shoemaker's brain transplant case with D. Parfit's critical remarks. The other methods that help to memorize and structure material better are the following: the creation of mind-maps, making philosophical vocabulary, and essay writing. The supervision is conducted by using Moodle testing tools. In [61], there is a more detailed study of using e-learning platforms in teaching philosophy.
The further perspective of the study is the practical realization of the implementation, planned for the next academic year. After adding the problem of personal identity to the course of philosophy, we plan to introduce this problem into other courses, especially in ethics, cultural studies, philosophy of education, and methodology and organization of scientific research.

Conclusions
We have suggested introducing the problem of personal identity in the course of philosophy. The analysis of the problem of personal identity shows that its subject area consists of such aspects: the nature and conditions of personhood, the metaphysical status of personal identity, the criteria of identity, and the method of thought-experiment.
The problem of personal identity has a long history of development: it was formulated implicitly in Greek philosophy, and it has been developing explicitly since Early Modern philosophy. The metaphysical status of personal identity is the question, if identity is the relation between person-stages over time or if it is the characteristic of the unified self. The problem of personal identity illustrates that the understanding of the concept of person has been changing since Early Modern philosophy. Nowadays, a person is considered to be a functional entity. A human being is a person, when it is involved in the process of selfconstitution, resulted in the emergence of personal identity. In analytic philosophy, there are two views on personal identity. According to the first, reductionist view, personal identity is grounded either on psychological or physical continuity. The non-reductionist view shows that no reliable criterion of identity. The method of thoughtexperiment emphasizes the weaknesses of the suggested criteria. It is used as the method of verification. Although the philosophers often criticize it for unrealistic scenarios, the method of thought-experiment remains productive in philosophy, with the help of which the teacher can present the problem.
The problem of personal identity has connections with topics of the course concerning the history of philosophy, metaphysics, theory of knowledge, philosophy of mind, and philosophical anthropology. Thus, there are several variants where to place the problem of personal identity into the course of philosophy. The paper proposes to introduce it twice: in the topic "Early Modern Philosophy", and in the topic "Philosophical Anthropology". The first introduction gives the outline of the historical background of the problem and helps to connect Cartesian philosophy and British empiricism. The further analysis of personal identity in the topic "Philosophical Anthropology", which is the per-last in the course structure, considers the problem of personal identity as the essential feature of personhood. The second turn to personal identity gives the students the possibility to refresh their knowledge of metaphysics, philosophy of mind, theory of knowledge and understand the material better.
The problem of personal identity is not highlighted well in Ukrainian philosophical discourse, so its implementation faces the lack of learning material in the Ukrainian language. That's why our primary task is translating primary sources and writing tutorials for the students.
The main method of introduction of personal identity in the classroom is the method of thought-experiment. There are some possible scenarios of thought-experiments on personal identity: "Brain Transplant", "Scattered Existence", "Bionic Replacement", "Teletransportation", "Branch-line", "Accident", "Indeterminacy", and "Fission". Such variety has great educational potential as the teachers can use these thought-experiments in different learning situations. We suggest analyzing William's and Shoemaker's puzzle-cases at the seminar. They are examples of the so-called fission scenario. The other methods used in teaching personal identity in the classroom are the following: the mind-map creation, making philosophical vocabulary, essay writing.
After the introduction in the course of philosophy, the problem of personal identity may be introduced in the structure of ethics, cultural studies (for the students of the bachelor's programme), philosophy of education (for the students of master's programme), and in methodology and organization of scientific research (for PhD students).