Philosophical argument concerning the elements of personal identity usually begin with examinations of the identity of the body, and later on, of the brain mind. Once it has been established that both the body and the brain mind of a particular individual remain constant over time, that person assumes an identity. This reductionist viewpoint, however, fails to consider the role of the immaterial soul in determining personal identity.
This theory, often called the Soul Identity Theory naturally assumes the belief in the existence of the soul,1 and holds that a person is only the same person over time if he or she possesses the same soul over that period. But the nature of the soul, even when accepted that it exists, is never universally agreed upon. Common beliefs, be they religious or no, often assume that over and above the mind, a person possesses a soul which exists beyond the death of the body, and which separates humans from other animals.
A traditional Roman Catholic perspective, as held by Aquinas2 for example, states that the soul is an indestructible3 and immaterial substance, which is simple,4 unchanging, and bestowed by God. Given that the soul is not a spatio-temporal object, and that it has not parts, the normal criteria for identity would seem not to apply, and thus in order to establish whether or not personal identity must rely on the continual existence of an immaterial soul the philosopher must look to new criteria and conditions for judgement.
5 Of the modern authors who have devoted time and effort to this problem, one of the most vocal supporters of Soul Identity Theory is Richard Swinburne. 6 In his dissertations, entitled “The Simple View”, Swinburne supports the belief that the soul is determinate regarding personal identity primarily with reference to his personal ‘abilities. ‘ Swinburne maintains that he can comprehensibly imagine existing in a disembodied state, where he can act on and learn about the world without the use of a specific body.
Given the logical possibility of such a notion,7 and given that a purely physical being could not hope to exist in this fashion, he must be more than a purely physical being. If Swinburne’s view is accepted, it can be seen that personal identity must indeed be tied to the existence of the soul, and furthermore, that one can exist as the soul, and not only in an earthly form. Standard Soul Identity Theory, as accepted by both Swinburne and his non-reductionist critics8 maintains that the soul is distinct from the brain mind.
Regarding this view, when it is considered that a person’s personality and thought patterns are associated with the mind, little room is left for the soul in determining personal identity. If a person’s life can be expressed through ‘person-stages’,9 and if these person-stages have a similar mind,10 body and brain, then surely that person remains the same throughout the period regardless of how many souls it experiences, or whether or not it experiences a soul at all.
If a soul remains after the death of its body, and if11 the soul is bestowed by God, then surely God could impart the same soul to two different bodies. 12 Thus, if it is claimed that Aristotle and Einstein shared the same soul, one might object that it is in no way obvious why sharing the same soul should make one person of what appear logically to be two. Furthermore, if the soul can exist beyond the death of its body, and is therefore not intrinsically tied to a particular ‘portion of matter’, then perhaps one ‘portion of matter’ may have more than one soul during the course of its existence.
Thus for example, if one purports that Winston Churchill was actually several successive persons,13 it may be stated that it is increasingly unclear as to why habitation of that body by different souls should cause him to be several persons over time. The crux of the concept here is the search for the criterion of personal identity which might make Winston Churchill the same person throughout his commonly agreed-upon person-stages,14 and logically this criterion seems to suggest that the continuation of the soul is not as important as the other more tangible aspects.
If a person has an indwelling soul which is bestowed at birth and exists after death, then one can wonder why a mind and body which doesn’t possess such a soul is not indeed a person. Here the onus falls upon the defender of such a viewpoint, such as Swinburne, to assert why in fact the soul (as essentially a gratis element) has anything at all to do with personal identity. Even if it is assumed that the soul helps determine personal identity, what then ensures that the soul which is present at various person-stages15 the same each time?
If it is in fact the soul which determines whether a person remains the same over time, then given that it is commonly claimed that one has no access to the soul,16 one can never know whether others are becoming different people every day. Soul Identity Theory causes many metaphysical and epistemological problems for the concept of personal identity, largely due to the fact that soul cannot be grasped in the way that the mind the brain and the body can.