What follows is an extract of an unfinished essay I began a few years ago.Philosophy has struggled to give a satisfactory account of personal identity, especially considering developments in science and scenarios in science fiction that have provided material for thought experiments. The rejection of the persistent self has ramifications for ethics. If I am a different person from the man who married Mrs X twenty years ago, am I under any obligation to keep vows that he made? In theological circles, this question has a bearing on the judgement of sin. Is God right to judge the person I am today for sins committed by “someone else” in the past? The unease that this question provokes has caused people of faith to re-engage with the question of selfhood and personal identity.
Modern cellular biology provided grounds for rejecting the view that the body was the source of personal identity. In the wake of this development, it has become necessary to seek less tangible hypotheses to account for personal identity and personal moral agency. The soul is an obvious candidate (in the case of those who believe in its existence). Nevertheless, is the soul a sufficient condition for personal identity? As beings of the physical plane, our sensory experience mediates our conception of reality. It is hard to conceive of existing without referring to concepts derived from physical objects experienced by means of the body. Should we then posit that both the body and the soul are necessary conditions for personal identity?
People of faith, believing in beings such as angels and demons, might respond that these entities are persons: they have will, memory, intellect, and emotions. Nevertheless, physical bodies do not define such entities in the way that they do humans – even if one admits that such entities have the power to assume physical bodies (cf. Gen. 6:1-6). The presupposition that physicality is not necessary for existence provides a foundation for belief in such entities.
Dreams and hallucinations provide another challenge to the body-soul theory of personal identity. Granted, physical bodies are necessary in order to have dreams and hallucinations. Neuroscience provides an explanation for chemical activity in the brain as the basis of these experiences. However, the point is not about the basis of the experience, but about its content, and the distinction between hallucination and perception. Perception (assuming the rejection of idealism), is an experience of the physical world: in perception, we are “connected” to the world around us. In what sense could we say that we are “connected” to the real physical world when we experience a hallucination? To be sure, we are in it, but we do not “experience” it as it is; we experience a fiction.
What does it mean to call the contents of a hallucination “fiction”? While one might quibble about the terminology, substituting words such as “unreal” or “untrue”, the point is that it is desirable to assert that what goes on in a hallucination is not an accurate representation of the external world near the subject at the time of the hallucination. This principle of “inaccuracy” allows the subject to categorize the experience as a hallucination after he has compared the content of his hallucination with the testimony of a reliable witness who was also present at the time. When this option is unavailable, the subject must either accept scepticism or depend upon another criterion or set of criteria to make an inference that the hallucination is in some way inconsistent with how the world is.
Now hallucinations and optical illusions have served as the bases for arguments against direct realism, often leading to indirect realism. For Descartes, dreams and the “evil demon” hypothesis, in conjunction with other reasoning, led to the conclusion that his existence did not depend upon a body. He was, however, unable to prove his claim that identity persisted from thought to thought: the evil demon could theoretically supply him with false memories. Even if one accepts arguments for the claims that God exists and that He is not a deceiver, if we acknowledge the existence of mental illness, personal, if not global, scepticism threatens. Mental illness replaces the evil demon in this paradigm. Further reasoning (and evidence?) is required to support the claim that I am not experiencing false memories and false perceptions.
The concept DECEIT (intentional misrepresentation) is necessary in order to understand and use the evil demon hypothesis, while the concept CONFUSION (vel sim.) is necessary in the case of the mental illness hypothesis. Both of these concepts presuppose a difference between what is “perceived” and what actually is the case. The subject does not require a previous “perceptual” experience with which to compare the present one. There are (at least) three reasons for this. Firstly, the subject may not be aware that he is having a deceptive experience: illusions can be subjectively indistinguishable from veridical perception. Secondly, in the case where the subject does believe that he is having a deceptive experience, the axioms or “experiences” that provide the frame of reference for the comparison and reasoning may themselves be false memories that the evil demon has supplied. Thirdly, the ability to analyse an experience may presuppose a set of axioms and abilities, and indeed the concept EXPERIENCE, but that does not entail that the subject must have had previous experiences.
Empiricism cannot be of help here. While empiricism claims the subject must have derived the concept EXPERIENCE from a particular experience (or set of experiences), experiences do not provide us with knowledge of the absolute but of the particular. That being the case, empiricism is unable to provide conclusive support for the claim that there is a substance persisting from one experience to another. Berkeley denied the existence of physical substance altogether, while Hume argued that the concept SUBSTANCE is the product of confusing the concept SIMILARITY with QUANTITIVE IDENTITY. Thus, the empiricist cannot demonstrate the synthetic claim, “I persist from thought to thought”, with deductive certainty, since it falls on the “matters of fact” side of Hume’s “fork”. At best, he can make a very compelling inductive argument. The possibility of scepticism remains. Rationalism, however, may offer a possible solution. The rationalist who holds to concept and knowledge innatism must accept the possibility that the evil demon has implanted false concepts and the illusion of knowledge in the (unsuspecting) subject. However, the rationalist may object that the demon must have persistent personal identity in order to force an illusion on the subject. Is this the case? Suppose that the demon has just winked into existence (spontaneous generation) – this itself is a leap, but is permitted for the sake of the thought experiment. The demon proceeds to create the subject, together with his false memories and axioms, and places him inside an illusion. In positing creation and the illusion as two distinct (but linked) moments, one is affirming the notion of IDENTITY, for the same demon persists from the moment he creates the subject to the moment he controls him in the middle of the illusion.