Waves, particles, free will, determinism

In a previous post, I reviewed The Chemistry of the Blood and Other Stirring Messages by doctor/pastor M. R. De Haan. In spite of the title, this was not a science book, but an example of the important genre of theological or philosophical reflection on science (the depiction of the pelican in medieval bestiaries is a past example of the genre).

Since then, I’ve been reflecting on more modern versions of the same theme. One obvious example is wave-particle duality. In the 1600s, Robert Hooke and Christiaan Huygens suggested that light is composed of waves:

This idea was confirmed by Thomas Young and others. This simplest proof is given by diffraction phenomena, such as the interference patterns produced by thin layers of air, oil, etc. (where “thin" means about a quarter of the wavelength of light – around 0.1 to 0.2 micrometres). Such phenomena only make sense in the context of light waves interfering with each other.

Interference patterns produced by the air gap between glass lenses (PD photo by “Ulfbastel”) and by a film of oil on water (photo by “John”)

An alternate theory, suggested by Pierre Gassendi and Isaac Newton, was that light is composed of particles:

This idea was confirmed by the photoelectric effect, where a particle (now called a “photon”) of light can “kick out” an electron from certain materials.

In a related phenomenon, a particle (photon) of light can alter the shape of a retinal molecule in the eye, triggering a cascade of events which ends with a signal being sent to the brain, reporting a flash of light (which is why you need vitamin A, to keep you supplied with retinal).

Light photons smashing into retinal molecules can alter them from bent (left) to straight (right)

The problem here is that light seems to be both waves and particles – which seems to be contradictory. It was only with the development of quantum theory that the wave and particle concepts were shown to be different aspects of a single (but rather complex) reality. This unification of seemingly contradictory viewpoints is known as wave–particle duality.

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A similar problem arises in theology. Calvinists are committed to both predestination and providence. In the words of Louis Berkhof, “Reformed theology stresses the sovereignty of God in virtue of which He has sovereignly determined from all eternity whatsoever will come to pass, and works His sovereign will in His entire creation, both natural and spiritual, according to His pre-determined plan. It is in full agreement with Paul when he says that God ‘worketh all things after the counsel of His will,’ Eph. 1:11” (Systematic Theology, p. 100).

No fate? On the contrary, the future is predestined.

At the same time, like other Christians, Calvinists are committed to free will in at least some sense. The call to “repent and believe” (Mark 1:15) implies the ability to exercise some kind of choice, and the Bible is full of affirmations that people are responsible for their actions.

To quote Berkhof again, “... the question naturally arises, whether original sin then also involves the loss of freedom, or of what is generally called the liberum arbitrium, the free will. This question should be answered with discrimination for, put in this general way, it may be answered both negatively and positively. In a certain sense man has not, and in another sense he has, lost his liberty. There is a certain liberty that is the inalienable possession of a free agent, namely, the liberty to choose as he pleases, in full accord with the prevailing dispositions and tendencies of his soul. Man did not lose any of the constitutional faculties necessary to constitute him a responsible moral agent. He still has reason, conscience, and the freedom of choice. He has ability to acquire knowledge, and to feel and recognize moral distinctions and obligations; and his affections, tendencies, and actions are spontaneous, so that he chooses and refuses as he sees fit. Moreover, he has the ability to appreciate and do many things that are good and amiable, benevolent and just, in the relations he sustains to his fellow-beings. But man did lose his material freedom, that is, the rational power to determine his course in the direction of the highest good, in harmony with the original moral constitution of his nature. Man has by nature an irresistible bias for evil. He is not able to apprehend and love spiritual excellence, to seek and do spiritual things, the things of God that pertain to salvation.” (Systematic Theology, p. 248).

This combination of doctrines produces exactly the same dilemma as with light waves and light particles. The answer must again be that both determinism and free will are aspects of a more complex reality.

Illustration of duality (image by Jean-Christophe Benoist)

Scottish theologian James Orr writes “A solution of this problem doubtless there is, though our minds fail to grasp it. In part it probably lies, not in denying freedom, but in a revised conception of freedom. For freedom, after all, is not arbitrariness. There is in all rational action a why for acting – a reason which decides action. The truly free man is not the uncertain, incalculable man, but the man who is reliable. In short, freedom has its laws – spiritual laws – and the omniscient Mind knows what these are. But an element of mystery, it must be acknowledged, still remains.” (Side-Lights on Christian Doctrine, pp. 30–31)

The element of mystery is explored in this famous hymn:

“God moves in a mysterious way
His wonders to perform;
He plants His footsteps in the sea
And rides upon the storm.

Deep in unfathomable mines
Of never failing skill
He treasures up His bright designs
And works His sovereign will.

Ye fearful saints, fresh courage take;
The clouds ye so much dread
Are big with mercy and shall break
In blessings on your head.

Judge not the Lord by feeble sense,
But trust Him for His grace;
Behind a frowning providence
He hides a smiling face.

His purposes will ripen fast,
Unfolding every hour;
The bud may have a bitter taste,
But sweet will be the flower.

Blind unbelief is sure to err
And scan His work in vain;
God is His own interpreter,
And He will make it plain. ” (William Cowper, 1774)