title: A critical analysis of Donald M. MacKay’s contribution to theology and science
Creators: name: Coghill, George M.
Publisher: name: University of Glasgow in partnership with the Edinburgh Theological Seminary
Year: 2023

description: In this dissertation I present a critical analysis of some of the philosophical and theological ideas of Donald M. MacKay. (1922–1987). MacKay was a Scottish scientist who made significant contributions across a range of scientific fields (information theory, artificial intelligence, and neuroscience), as well as to the discipline of theology and science. His main contributions that I explore are Complementarity and Logical Indeterminism, both of which highlight the importance of standpoint for what one says about a subject. Complementarity identifies two,or more, descriptions of a common referent as each being complete and exhaustive with respect to their own language, but saying nothing about the other. MacKay described two types of complementarity. The first is nonhierarchical, an example of which is the projection of all the points of a three dimensional object onto two, or more, two dimensional planes: the points on the planes are in a complementarity relation to each other. The other is hierarchical, examples of which are the physical and informational descriptions of a communicated message (the sign and the things signified) and also the relation between the non-hierarchical descriptions and the original object. He used this, amongst other things, to suggest a relation between scientific and theological perspectives; but also, as he moved into neuroscience, to argue for a nondualist approach to the mind-body problem(which he termed “duality without dualism”). It turns out that hierarchical complementarity, as MacKay presents it, has the same basic definition as supervenience. However, I argue that hierarchical complementarity can be revised to make it a more general relation that is better suited than supervenience to issues of religion and science, particularly free will and determinism. The other of MacKay’s main contributions was to propose a solution to the problem of free will and determinism. He called this Logical Indeterminism. Here MacKay supposes, for the sake of argument, that hard determinism holds. He posits a thought experiment in which one can use a instrument, which he calls a “cerebroscope”, to view every detail of a brain and it’s behaviour. It turns out that in such a world it would be possible for an external observer to identify a complete specification of the brain state, but for the owner of the brain this specification would not exist. From this he argues that a “superscientist” could, from their standpoint, use the observation of brain state (also making use of the complementarity of brain and mind) to predict what the observed agent would do in their immediate future. However, because that observed brain state does not exist for the cognitive agent whose brain is being observed, the predicted behaviour does not have a “claim to their assent” until after they have made up their minds what they are going to do. As such the future remains open for them, and so they are free in a very real sense. In my analysis of MacKay’s argument I find that in its current form it is guilty of the modal fallacy. However, by making it more explicitly modal this issue can be overcome such that it then achieves what MacKay claimed for it. MacKay also suggested that Logical Indeterminism entails that the Godhead must be multi-personal. This was with respect to the economic Trinity. I suggest that the modal version entails that the Godhead must be ontologically multi-personal in a manner that fits with classical Christian theism.