Neurologists tell us that our brains function laterally: certain activities are associated with one side of the brain and not the other. For example, analytical problem-solving activities appear to engage mostly the left side while intuitive artistic activities engage the right side. This leads to individuals being characterised as left-brain persons as against right-brain persons depending on whether they are hard-nosed or soft-nosed (analytical or intuitive) in temperament.

We need to be very careful in following this line of discourse. To begin with, saying that someone is right-brain dominant instead of saying that he or she is artistic in temperament is not telling us any more about that person than we already know. It is rather like taking a proposition written in English and then translating it into Latin. This may indicate that we have had the benefit of a classical education but it does not really add anything to the original observation.

More critically, it can lead us into false conjectures. We usually think of our physical characteristics as being genetically determined-baby has Dad's eyes and Mum's nose-and it is an easy step to suppose that a genetically-determined brain structure will lead baby to have certain behavioural characteristics too. In the not-too-recent past such a line of reasoning led to the claim that persons with criminal tendencies could be detected (and thwarted) simply by measuring the bumps on their heads. Today, phrenology continues to fascinate some people but its practitioners are usually found only in funfairs.

When we come to consider experiences like sensations, thoughts and feelings we find the same tendency to explain mental activity in terms of physical structure. (This is, perhaps, because material objects are somehow more tangible than immaterial ones.) Thus we know that as our neurological system responds to light of a certain wavelength we have the immaterial experience of seeing red. But we should avoid concluding that it is therefore only the neurological response that is real and not also our experience of redness.

The claim that mental experiences are (or will be when we have sufficient knowledge) ultimately reducible to physical structures and forces is known as reductionism. Reductionists claim that all mental activity can, in principle, be explained in terms of biochemical and bioelectrical patterns in our brain, and that is where reality really lies. The immaterial mental world, by contrast, is not quite real.

Does this matter to us as Christians? Yes, it does, because, if the mental world goes, the transcendental world will not be far behind. As Thomas Jefferson put it in 1820: "To talk of immaterial existences is to talk of nothings. To say that the human soul, angels, god, are immaterial, is to say that they are nothings, or that there is no god, no angels, no soul."

We claim that belief in transcendence, and hence in God, is rational. We ought not to undermine that position by allowing reductionism to creep into our discourse unawares. Ill-considered talk of left-brain persons and right-brain persons inevitably leads us along that slippery path.