Portrait of Marcel Duchamp, Jacques Villon (1875–1963).

This essay begins with a presentation of the mind renovation thought experiment. The essay goes on to present an argument based on constituent identity as a solution to the thought experiment. The essay then introduces and replies to counterarguments to the assertions put forth. The essay finishes with a summation of its argument and a final commentary on the nature of identity.

The thought experiment supposes that Person A, hence forth called Jack, sits in a chair. Whilst seated a clinician takes a copy of Jack’s mind before proceeding to replace one-thousandth of Jack’s mind each second. Thus at the end of a thousand seconds a new mind replaces Jack’s mind, hence forth called David. At the same time Person B is having their mind replaced. The clinician errs during Person B’s mind replacement and Person B must have their mind returned to the copy taken before replacement began. The clinician grabs Jack’s mind-copy by mistake and replaces Person B’s memories with those of Jack. Thus at the end of a thousand seconds Jack’s mind inhabits the body of Person B, hence forth called Jill. The thought experiment ends by asking whether David, Jill, both or neither are Jack — the question this essay seeks to answer.

To answer the question a definition of Jack is necessary. A definition of an individual’s identity. Each identity comprises a self-representation and an other-representation. The self-representation is one’s identity as seen by oneself. The other-representation is one’s identity as seen by others. Each of these representations consists of two components, the mental and the physical. Any change to one or both of these components causes a change in the representation, and thus the identity. These physical and mental components undergo change over time. An individual’s experiences will leave traces on the physical and mental components. Thus one’s self- and other-representation are in constant flux.

One might object that the identity is comprised of more than the physical and mental components. That at least a third component exists, such as the soul or spirit. This objection collapses under the definition of identity. An individual’s other-representation is comprised of sense data and ideas expressed by the individual. An individual’s self-representation is comprised of sense data and ideas within the mind. A component that exists outside of these realms of idea and sensation would be unable to affect one’s self- or other-representation and thus their identity.

Despite the instability of identity, our language uses only one term to express one’s self- and other- representations. The term ‘I’ captures the self-representation. The unique ‘I.’ As an individual’s self-representation changes the term used remains the same. An individual’s name manifests the other-representation only when in the context of the specific individual. Whether an individual is one or one hundred years old, fascist or communist they are identified by themselves as ‘I’ and others by their name. The name is a mere simulacrum of the composition of the self- and other-representations. A composition of the mental and physical.

Jill possesses the mental identity of Jack. In terms of mental self-representation, Jill considers herself to be Jack. In terms of mental other-representation, a Turing test is required. Consider Jill hidden and only able to communicate through a computer screen using text. The outside observer with knowledge of Jack’s mental other-representation would consider Jill to be Jack. When Jill is revealed to the observer would their supposition prove false. Whilst Jill has the mental identity of Jack she does not have the physical identity. This does not match the outside observer’s complete other-representation of Jack. Hence, they would not consider Jill to be Jack.

David possesses the physical identity of Jack. In terms of physical self-representation, David considers himself to be Jack. In terms of physical other-representation, a reverse Turing test is required. Consider David revealed but unable to communicate through a one-way mirror. The outside observer with knowledge of Jack’s physical other-representation would consider David to be Jack. When David is able to communicate to the observer would their supposition prove false. Whilst David has the physical identity of Jack he does not have the mental identity. This does not match the outside observer’s complete other-representation of Jack. Hence, they would not consider David to be Jack.

The original identity of Jack is the composition of both the physical and mental. To be Jack, to one’s self or to others, one requires both elements. Separating one element from the other causes the disintegration of the whole. Both David and Jill fail to correspond in their entirety to the identity of Jack. The identity of Jack has been in constant flux since its creation. Both the physical and mental components of one’s identity undergo change over time. The difference is the abruptness of the change. The complete separation of Jack’s identity causes problems that the self and other must then reconcile.

Jill possesses the mental identity of Jack. The mental representation of an individual identity has greater value to the individual. Jill will judge herself to be Jack. Consider amputation of a limb. Despite the abrupt change to one’s physical identity they will still consider themselves to be themselves. So it follows that Jill’s mind will follow the same line of thought. Jill’s self-identity will change to accommodate the physical. The self-representation of Jack will reside in Jill.

David possesses the physical identity of Jack. The physical representation of an individual identity has greater value to the other. David’s other-identity will change to accommodate the mental. Others will judge David to be Jack. Consider exposure to and agreement with an idea contrary to an individual’s psyche. Despite the abrupt change to one’s mental identity others will still consider the individual to be that individual. So it follows that the minds of others will follow the same line of thought. David’s other-identity will change to accommodate the mental. The other-representation of Jack will reside in David.

One may object to the ontological valuation of the physical and mental components. One might also object to the accommodation of the self- and other-representations by David and Jill. An individual may consider the physical to be of greater importance to their own identity. Another may consider the mental to be of greater importance to another’s identity. This is irrespective of the result. Regardless of the ontological value placed on the physical or mental components. Regardless of the accommodation of the self- and other-identity. Both Jill and David fail to encapsulate the entirety of Jack’s identity.

Jack’s identity has been torn between Jill and David. Both of have experienced abrupt changes to their identities. Jill with regard to mental representation of Jack. David with regard to physical representation of Jack. The accommodations made by Jill and David have destroyed the original identity of Jack. Despite the changes to both Jill and David, respective of Jack, the referring terms have not changed. Both Jill and David will still call themselves the individual ‘I.’ Others will still call David ‘Jack.’ Others will still call Jill ‘Person B.’ For the name is a simulacrum of the self- and other-representations. A simulacrum of identity.