On the 28th May 1944, the writer C.S. Lewis gave a talk in the chapel of Mansfield College, Oxford as part of a Pentecostal celebration. His talk is reproduced in essay form in a subsequent collection of Lewis’s talks in The Weight of Glory”, under the title Transposition.

Paying tribute to the occasion, Lewis begins with a discussion of glossolalia– the phenomenon of “speaking in tongues”. Lewis acknowledges that he’s in no position to deny the stated experiences of St Paul (who claimed such an experience, on several occasions), and then moves on to do what any decent guest does when embarrassed by his host: he changes the subject. In this case by introducing a set of themes connected to the nature of language in general, and the metaphysical implications which always attend it.

When a transposition takes place, it is not the case that the “higher” concepts can be mapped smoothly onto the “lower” ones

The themes are these: the nature of the relationship between Earth and Heaven; the status of the Incarnation; the distinction between symbolism and sacramentality; and the possibility (which he does not accept) of identifying the mind with the brain.

It’s the last of these I’ll focus on – not because the Incarnation is not interesting (how could it not be?), but because it’s often occurred to me that Lewis is revered as a writer but overlooked as a philosopher. Distributed within Transposition is what I take to be an effective and prescient objection to the thesis that the mind and the brain can be one and the same thing. And I’m going to suggest that a thought experiment he deploys anticipates a famously inventive complementary thought experiment which objects to the assumption that they could be.

 What does Lewis mean by “transposition”?

A transposition occurs, he argues, when a richer set of conceptual categories must necessarily be represented by a poorer set of conceptual categories. Or as he puts it, when a “richer” medium must be adapted to a “poorer” one:

If you are to translate from a language which has a large vocabulary into a language which has a small vocabulary, then you must be allowed to use several words in more than one sense….If you are making a piano version of a piece originally scored for an orchestra, then the same piano notes which represent flutes in one passage must also represent violins in another.

When a transposition takes place, it is not the case that the “higher” concepts can be mapped smoothly onto the “lower” ones. As Lewis puts it, the relation is algebraic and not arithmetical.

But even that doesn’t capture it- when a transposition occurs there is an animation occurring between “higher” and “lower” such that the “lower” is enriched by the “higher”.

Examples would be these: when the same set of feelings in the gut accompany the very higher (and very different) sensations of love and lust; when the same poem ignites in you a physical feeling of joy and then ten minutes later -after she has dumped you- the same feeling reveals itself as despair.

“It is clear that what is happening in the lower medium can be understood only if we know the higher medium”.

Lewis has an example, in the form of a thought experiment:

Let us construct a fable. Let us picture a woman thrown into a dungeon. There she bears and rears a son. He grows up seeing nothing but the dungeon walls, the straw on the floor, and a little patch of sky seen through the grating….This unfortunate woman was an artist, and when they imprisoned her she managed to bring with her a drawing pad and a box of pencils…As she never loses hope of deliverance, she is constantly teaching her son about that outer world which he has never seen.

Eventually, the woman confesses to the son that the world outside is not really comprised of pencil marks but has a “solid” reality of its own. At which point the son loses his grasp on any conception of the world outside of the dungeon. Lewis’s point is that he’s only been given one side of the transposition.

Lewis uses the experiment in a cautionary way, not least in his warning that theologians have a habit of talking about Heaven merely in terms of one side of the transposition: if, as Aquinas argues, we can only approach God by analogy then there is a danger of thinking that the language of the analogy is the real thing: hence we tend to think of the Kingdom as being populated by family and as lubricated by a currency of gold, because these are the easy part of the transposition.

But back to the philosophy of mind.

In a paper published in 1986 the Australian philosopher Frank Jackson, arguing against the idea that the mind and the brain can be one and the same thing offered the following thought experiment:

Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like “red”, “blue”, and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence “The sky is blue”. … What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not?

The usual interpretation of Lewis’s dungeon thought experiment is that it is a version of Plato’s allegory of the cave. That seems to me to be inaccurate. In Lewis’s example the instinct in the direction of a higher realm is left scattered and destroyed by the mother’s inability to convey her side of the “transposition”. Plato would have it as a given that we have a residual memory of that world. 

The Jackson version seems more plausible to me, the only difference being that Mary has more of a chance in life than the boy in the dungeon. She is at least released from her own high-tech prison and when she is, by hypothesis, she learns something: what it is like to have a “higher” set of conceptual categories -those relating to the nature of colour-experience- and how she was robbed of those experiences by the other side of the “transposition”.

It was entirely usual that Lewis anticipated arguments that were formalised some years “down the pipe” by the allegedly more “analytical” philosophers. Would it be an impertinence to stretch a point and suggest that the Jackson types are, themselves, transpositions from a higher wisdom?