All in the Mind?

Does neuroscience challenge faith?

Peter Clarke

• Verlag: Lion Books
• Jahr: 2015
• ISBN:
  9780745956763
• Auflage: 1
• Thema: Theology & Religion
• Thema: Religion & Science

Much progress has been made to understand the intricacies of the brain's workings. Some have claimed, and many assumed, that these findings have challenged faith in God to the point of destruction. Are we not mere neural machines? Are religious experiences not just 'in the mind', the products of abnormal 'brain events'? Is faith not just a side effect of evolution? Not so, according to neuroscientist Peter Clarke, after a lifetime's study of the brain. In this comprehensive book, the current state of neuroscientific evidence is weighed up alongside ideas of what it means to be human, the idea of the soul, near-death experiences, and questions of free will and responsibility. He engages with the leading thinkers in these areas, including Francis Crick, Richard Dawkins, Daniel Dennett, Sam Harris, and Daniel Wegner.

APPENDIX 1

Quantitative Problems with Quantum Libertarianism and Quantum Dualism

This appendix deals with some technical issues relevant to Chapter 5 (where I discuss quantum libertarianism – the claim that the fuzziness of quantum theory may provide the indeterminism required by libertarianism) and Chapter 10 (where I discuss quantum dualism – the claim that this same fuzziness provides a tiny gap in the causal chain allowing soulish influences to affect the brain). I here focus on quantum dualism, but the main arguments and calculations are relevant to quantum libertarianism as well.

The reason why people invoke quantum dualism is to try to solve the problem that soul–brain interaction would require a violation of the laws of physics. The only way of solving this problem that has any modern support is the suggestion that the fuzziness (indeterminacy) of quantum physics (see below) provides a kind of leeway within which very small soul-induced perturbations would be possible (quantum dualism). Numerous objections to it have been advanced by many people including me. In this appendix, I discuss just one of the objections: the problem that the indeterminacy is too small to allow significant effects on neurons.

Quantum Physics

Quantum physics (also called quantum mechanics or wave mechanics) is the branch of physics that deals with atomic and subatomic (micro-scale) phenomena. It was founded during the first 30 years of the twentieth century because classical physics was unable to account for certain micro-scale phenomena. One of its important claims is that very small particles such as electrons should be thought of not as miniature billiard balls but as semi-localized waves. If you find this counterintuitive, you are not alone. In fact, one of the great founders of quantum physics, Niels Bohr, once said, “Anyone who is not shocked by quantum theory has not understood it.” It would be beyond our present scope to go into the details, so I shall jump rather abruptly to the part of it that tends to be invoked by quantum dualists wanting to solve the problems of soul–brain interaction.

Heisenberg’s Uncertainty Principle*

The fact that small particles are semi-localized waves implies that their position, energy, momentum (mass × velocity), and so on are defined only approximately. In other words, they are “indeterminate”. There are various forms of this quantum fuzziness, but we here focus on its best-known expression in Heisenberg’s famous uncertainty principle, which states that there is a limit to the precision with which the momentum (p) and position (x) of a small particle could be simultaneously measured, given by Δp.Δx ≥ h/4Π where Δp and Δx express the indeterminacy of the momentum (p) and distance (x), and h (Planck’s constant) = 6.63 × ^-34 joule seconds (Js). Thus, the precision limit applies to the product of the two variables. The more precisely one is measured, the greater the imprecision for the other. Other versions exist, applying to different pairs of variables, for example energy (E) and time (t): ΔE.Δt ≥ h/4Π. Since h is very small indeed, Heisenbergian uncertainty is of no relevance to macroscopic objects such as golf balls; but it is very relevant to submicroscopic entities such as electrons and photons.

Thus, there is an inevitable trade-off between the measurement precisions for position and momentum, or for time and energy. For this to serve the needs of quantum dualists, they need to make the further claim that this is not just a problem about the practical difficulties of precise measurement, but is a fundamental statement about the nature of reality. Reality itself is fuzzy. This claim was hotly disputed by Einstein, but it is currently accepted by most physicists and philosophers, although still debated. Let us accept it provisionally, to see how the quantum dualists try to use it.

Quantum Uncertainty at Synapses

The relevance of this to our present concerns stems from the idea that quantum fuzziness might undermine the determinism of brain function. This has been seized on by advocates of libertarian free will, who believe that brain indeterminacy is required for free will (see Chapter 5), and by quantum dualists (our present concern). I shall focus on the publications of Sir John Eccles in collaboration with physicist Friedrich Beck, because these are generally recognized to provide the most plausible (or least implausible) version of quantum dualism.

The synapse is the cellular location for mind–brain interaction most commonly proposed by quantum dualists, including their most eminent advocate, the late Sir John Eccles. One reason for this is that they think the soul/self/mind would need to influence conscious decision-making directly and immediately. Another is that Eccles thought the synaptic vesicles (the tiny – about 50 nanometres – membranous sacs that contain the neurotransmitter) were small enough to be subject to quantum effects, although this is now known to be untrue.

Eccles published numerous versions of his interactionist model, refining them in the light of criticisms, and the best is considered to be the version he published in collaboration with physicist Beck, involving quantum tunnelling of unspecified “quasiparticles” between the thin membrane surrounding the synaptic vesicle and the presynaptic membrane.¹ Since this model was first proposed, some of its biological details have turned out to be incorrect, and its quantitative aspects were criticized by neurophysiologist David Wilson.² Wilson further argued that it would be less implausible to postulate Heisenbergian effects on the control of presynaptic calcium concentration rather than on the movement of synaptic vesicles. However, the following argument, which I have adapted from Wilson and elaborated in more detail elsewhere,³ indicates that Heisenbergian effects are still much too small.

As a specific example, we consider whether a fluctuation within the limits of Heisenbergian uncertainty could affect the presynaptic calcium concentration by changing calcium flow through ion channels in the presynaptic membrane. For this, it would need to modify chemical bonds in the channels. According to Heisenberg’s principle, the precision limit to the energy (E) and time (t) is given by ΔE.Δt ≥ h/4Π where h = 6.63 × 10^-34 J.s. To have even a minimal effect on the presynaptic calcium concentration, the ion flow would need to be changed for at least 10 microseconds, probably much more. Substituting this value of Δt gives a ΔE of about 5.2 × 10^-30 joules (J), which is about 200,000 times too small to disrupt even a van der Waals interaction, the weakest kind of chemical bond (E = 1 × 10^-24 J).

Another problem is that the energy uncertainty (ΔE) is about a thousand million times smaller than the energy of thermal noise. Owing to the non-zero temperature of the body, every molecule (and every part of every molecule) is constantly moving in a way that is not controlled by the cellular control mechanisms. The problem of this for quantum dualism is that any soul-mediating effect of Heisenbergian uncertainty would be swamped by the far greater energy of the thermal noise. Furthermore, to be able to cope with the thermal noise, all cells (including neurons) and all organs (including the brain) have noise-resistance mechanisms, as I have discussed in detail elsewhere.⁴ If these can make the cells resistant to thermal noise, they should be more than sufficient to ensure resistance to Heisenbergian uncertainty.

It is sometimes argued that the effects of Heisenbergian uncertainty might be amplified. There are many problems with this, not least that the amplification mechanism would have to increase the effects of the Heisenbergian uncertainty but not those of the thermal noise, which seems implausible. There are other problems as well, beyond our present scope, and I have argued in more detail elsewhere that amplification is unlikely to provide the indeterminacy required for quantum dualism.⁵

These are not the only quantitative problems with quantum dualism. Others have been discussed by Smith.⁶ All in all, the quantitative case against quantum dualism seems to me strong, and I can only see one possible opening for counterarguments. This is that indeterminate quantum fluctuations much greater than those predicted by Heisenbergian uncertainty are theoretically possible.⁷ The warm, wet environment of a biological organism tends to make such events exceedingly brief, but recent evidence indicates that they can have significant effects in certain biological situations, notably photosynthesis and magnetic field sensitivity. ⁸ Such effects have never been shown in neuron-to-neuron communication or in any aspect of brain function, but this is a new field, so we must wait to see what the future reveals.

In conclusion, apart from a faint flicker of hope offered by new data on quantum indeterminism above Heisenbergian levels, quantum fuzziness seems to be too limited to provide a plausible leeway within which a separate Cartesian soul might influence the brain. This is not where I would lay my bets!⁹

APPENDIX 2

Neo-Darwinism and Why I Accept It

The overwhelming majority of biologists accept the current version of Darwinian evolution, known as neo-Darwinism, which is by definition the “modern synthesis” of Darwinian evolutionary theory with genetics. I here explain briefly the main tenets of neo-Darwinism and why I accept them. It would be beyond our present scope to tackle the subject in depth, and I do not expect by the following few words to convince opponents of neo-Darwinism to change their minds. But I think I owe it to sceptics about evolution to address briefly current evolutionary theory and explain why I accept it, since I assume its truth in Chapter 13 on religion, because the entire scientific literature on the latter takes for granted the truth of neo-Darwinism.

The Two Components of Darwinian Evolution

Darwin’s theory of evolution involves two separate claims: evolution by common descent and natural selection (Figure A2.1).

Evolution by Common Descent

This is the claim that the ...