There are three main ways in which we can think of a person.

The first and least problematic is to identify a person with a body.  We can refer to a particular human body using the tag of an individual’s name and there is no ambiguity about the individual concerned.  A body remains clearly the same biological entity, despite its growth, decay and changes over the years.

The second conception is an internal, psychological one.  I can think of myself as my mind over time as linked by memories, character, narrative and plans.  From my subjective view I can see my experienced life as unfolding in a fairly unified way.   

And the third concept is to think of the self as a fixed experiencer, a soul, that sits in the experiencing mind and ‘has’ the mind’s perceptions and thoughts.

Current mainstream philosophy and science agree that the third concept is a mistake.  A good reason for this is that souls are not seen.  We may think we have a fixed experiencer, but if we try to introspect, we can’t find any such thing.  As David Hume wrote in 1738: ‘I never can catch myself at any time without a perception and never can observe anything but the perception’ so for him a person is ‘nothing but a bundle of different perceptions.’

Neuroscience has also failed to find souls.  The scientific picture is that there is no fixed centre of consciousness but rather consciousness arises from distributed processing around the brain.  The underlying brain teems with activity, of which certain elements are promoted to contribute to conscious awareness.  Consciousness is constructed by the brain as a kind of user interface to monitor the activity of the brain and direct its attention.  The brain constructs the user interface so that consciousness appears as a single stream with a unified nature.

So, both introspection and neuroscience fail to find souls.  Further doubt arises on considering what a fixed experiencer would involve.  If it is immaterial, then it is a mystery how it interacts with the physical world in receiving perceptions and willing action. If it doesn’t interact, then it wouldn’t matter whether a person had none, one or a hundred souls.  If it interacts, then the experiencer can be caricatured as a little man, a homunculus, that ‘sees’ the mind’s perceptions as projected in a kind of theatre.  But this gives a regression problem as it needs to be explained how the homunculus experiences without having a further homunculus inside itself.

Despite the failures to observe souls, and the philosophical problems they would involve, the fixed essence concept is very natural and tempting for us. We can see reasons why the concept may persist even if it is wrong.  It may persist partly because our brains construct such a strong impression of our own unity that it is natural for us to assume that this is caused by us having a single underlying essence.  Our language also confuses: we assume that “I” as a noun must refer to some fixed thing.  More deeply, it is suggested that we have evolved to conceive of ourselves as having a soul as this has been an efficient way to centre our thinking and to survive:  constructing a model of ourselves as having a soul has been useful if not necessarily true. 

Although the fixed essence concept is now commonly rejected by philosophers and scientists, this hasn’t always been the case.  Descartes famously argued that although any of his individual perceptions could be erroneous, the one thing of which he could be certain is that he is thinking – ‘I think therefore I am.’  From this he developed his dualistic view that minds are of an immaterial nature distinct from physical matter.  But Descartes assumed too much:  introspection can only show that there is a thought happening when ‘I think’ and cannot show that this thought is had by an ‘I’ that is a soul.  

The dismissal of souls is a clear achievement of philosophy.  Humans evolved to conceive of themselves as having souls but philosophy supported by science has shown that this does not reflect reality so we should think differently.  Unlike on other issues where philosophy uses involved arguments for its challenges to instinctive thinking, the dismissal of souls is based on introspective and scientific evidence which anyone should be able to appreciate. Yet, most people still continue to have the concept of a soul, which can then give credence to views of reincarnation and life after death.  There is a job to be done to spread the word of the clear view from philosophy and science that it is a mistake to consider we have souls.

If we drop the concept of a person as a soul, we are left with the bodily and psychological concepts.  Both are important – the bodily concept to identify a person within society and the psychological one for the individual himself and those close to him.  That the bodily concept is not enough can be illustrated by how we regard an individual in infancy and after severe brain damage as in some ways not being the same person when they are not linked by memory and psychological continuity.  

The simple fact that people change over time should be recognised in how we use the psychological concept.  Whether someone is the same person should be seen as a matter of degree.  People are complicated, they change with age, health and circumstances and display different facets; memory is often misleading. 

Am I the same person as my 10-year-old self?  In the sense of having the same identifiable body: yes.  In the sense of psychological continuity: partly.  In the sense of having the same soul: no such thing.