6.5 Identity, change and essence

A perennial problem in philosophy has been to find a concept of ‘substance’ as that which persists through change. A similar problem is to define the ‘essence’ of an object: that which defines the characteristics of an object that must be kept through all changes in order for the object to be the ‘same’. In both cases we want to consider living organisms and humans. What is the essential part of a person that remains with him unchanged through his entire life? Is there such a part to define his identity? Philosophers have debated whether it is some kind of mental being which does this, such as a soul, or whether it is done by the existence of memories, or whether personal identity should be based on the continuity of bodily existence. Many of the same questions occur in physics and psychology. They come to the fore when we consider non-trivial changes such as brain transplants, body transplants, and especially when trying to understand post-mortem survival and the ‘resurrection of the body’. This section confines itself to the simple question of how we recognize the essence of a particular substance or being and how it might retain (or not) its identity through change. Applications to psychology and theology will be deferred to Chapter 20.

We are able to extract a first sense of identity when we base our analysis on the concepts from Chapter 4 where the substance of a thing is simply its fundamental dispositions. This is a strict identity, where a substance keeps exactly the same properties for a non-zero duration of time. The finite duration of a disposition before another event was how we first identified it as a candidate for what a substance might be. At the moment we do not know, for a given substance, whether this duration is a nanosecond or a millisecond. That will require empirical investigations. All we have established is that it is logically possible that there is some kind of identity over a non-zero time interval.

A second kind of identity, over a larger interval, one that includes multiple events, may also be possible, if the disposition itself does not change. We are referring to changes in the disposition itself that are not relations between it and something else. We are talking about the disposition in its internal character or essence. The exact nature of that internal essence will have to be clarified empirically. For now we only observe that it is logically possible that a disposition can act, and yet itself be not internally changed by the acting, qua disposition. A charged electron can repel another, for example, without the electron being changed in the sum of its fundamental dispositions. Other properties (e.g. recoil velocity) may still change, but the charge-disposition itself does not need to change. If this pattern is instantiated in the real world, then we have a longer duration of identity which can be established for objects. Identity may be obtained if objects exist continuously for that duration and do not change the nature or measure of any of their underlying dispositions, namely the fundamental dispositions that constitute the substance of that being. What are excluded in that duration are changes which do modify those fundamental dispositions. An electron colliding with a positron, when both charges disappear and are replaced by two photons, would be an example of such a change (even a termination) of identity.

The first sense of identity is very strict, and the second is not so strict, but neither is adequate to determine the continued identity of a composite object, where this might be an atom, a molecule, an organism, or a person. There does seem to be a continued sense of identity for some of those beings, a sense of ‘numerical identity’ that persists through the many changes that organisms and people undergo while growing and living their lives. We claim that for people there should be such a generalized sense of identity. Hume was skeptical about the existence of any such sense, but we intuit that we do remain ourselves and do not become another. Is there a further generalized sense of identity which may be possible in our dynamic ontology?

With the concept of generative levels, there is indeed a new kind of identity relation that we might find relevant to persons. Consider the possibility of an organism B that is part of a structure of generative levels, such that disposition A is that which generates the powers and capabilities of B. When the organism acts, these powers produce effects C, which we may for simplicity consider the final definite actions in the world. The are thus multiple generative levels in the sense of Chapter 5.

Suppose now that level A experiences many fewer changes than does B, so that it is a comparatively long time between changes that change the substantial dispositions of A. Further consider the fact that, within generative levels, the level A is the cause of all the dispositions that B has and may indeed be called ‘responsible’ for B. The details of B depend entirely on A itself and on the details of the circumstances that occasion the operations of the dispositions of A and B. In this case, an argument can be made that there is a ‘true persistent identity’ that can be ascribed to B, namely the prior degree A itself. There is a sense, therefore, in which A can be considered the ‘true nature’ or the ‘source of activity’ of B and hence its true underlying identity. This underlying identity will last as long as the ‘comparatively long time’ (mentioned above) between the substantial changes of A.

Therefore there exists a third sense of underlying identity which can be given to objects that exist as one of a set of multiple generative levels. Any of the prior degrees could be identified as the ‘true underlying identity’ of that object. In a loose sense, the words ‘essence’ or ‘true nature’ could be extended in meaning to one of the prior degrees, as could the word ‘soul’ in Plato’s sense as the ‘source of motion’ of an object. We will see later that such descriptions make sense within a context of theism. Theism is therefore the next subject to be discussed.