What is Life? (1) An Evaluation of Several Possible Approaches to This Question

Technological advances over the last centuries have extended the horizon of possibility for scientific achievements in many fields of human inquiry. In light of such advances, many people today hold that both the synthesis of artificial life, and the discovery of extraterrestrial life, are within the scope of possibility for the near future. For many people, the discrepancy between realising these achievements and the present moment appears to be entirely a function of technology. It is imagined that continuing developments in genetic engineering and molecular research on the one hand, and space travel and research on the other, will resolve all of the current obstacles in respect to these possibilities. Such an assessment may not be entirely accurate, however. In respect to the possibilities above—of synthesising and discovering life—we must ask ourselves how we would recognise novel forms of life in the first place. What is life? Quid est vita? This question stands like the Sphinx’s riddle at the frontiers of technobiological discovery.

One possible approach to this question is to conceptualise life in terms of chemistry and physics. Thomas Mann famously expressed this approach his 1923 novel The Magic Mountain. In a conversation between Hans Castorp and Hofrat Behrens, after concluding that death is essentially “oxidation,” Castorp poses a question to the medical director,

“And life?”

Behrens replies, “That too, my lad. That too is oxidation.”

Behrens continues, “Life is primarily the oxidation of cellular protein. That’s where our pretty animal warmth comes from, of which some people have a bit too much. Ah, yes, life is dying—there’s no sense trying to sugar-coat it.”

To define life in terms of physical and chemical processes confers the immediate benefits of convenience and accuracy. By establishing a quantitative standard, such an approach provides for direct verification by measurement against this standard.

At the same time that Behrens enunciated the chemical definition of life in The Magic Mountain, scientists in other fields were formulating analogous conceptions. The physicist Erwin Schrödinger, for instance, famously introduced the notion of life as thermodynamic relations amongst gradients of entropy. In his 1943 monograph “What is Life?” Schrödinger explored the possibility of such a conception. Despite his enthusiasm and speculative ingenuity, Schrödinger ultimately arrived at the belief that a definition of life in terms of physics could never present a complete account: “living matter, while not eluding the ‘laws of physics’ as established up to date, is likely to involve ‘other laws of physics’ hitherto unknown, which however, once they have been revealed, will form just as integral a part of science as the former,” he wrote.

The possibility that Schrödinger had explored again reached public attention some seventy years later through the work of the physicist Jeremy England. In 2013, England revealed a theory of abiogenesis (i.e. the origin of life from lifeless processes) that could account for the origin of life in purely thermodynamical terms. Specifically, England postulated that inert atoms will spontaneously reorganise themselves in order to dissipate thermal energy with greater efficiency: “you start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant,” England explained in a interview in 2013. Life—in its ontogeny, phylogeny, and operation—“should be as unsurprising as rocks rolling downhill,” England continued.

Despite the vision and optimism of England’s theory, we should not allow its promise to enrapture us at the expense of thinking it through in a thorough manner. Even if we suppose that future experiments corroborate the accuracy of England’s theory, we must still wonder whether it has really accomplished what it claims. Let us explore this question. To explain the origin of life implies that one has defined the nature of life. Despite the hope of a thermodynamic solution to this question, it remains only a possibility and therefore NASA’s working definition for life is not a thermodynamic one. In 1993, NASA had appointed a council of scientists and charged it with generating such a working definition of life. The fruit of this convention was the following:

[life is] a self-sustaining chemical system capable of Darwinian evolution.

Thus, England’s theory posits that the basic characteristic of matter to arrange itself in configurations that increase its efficiency to dissipate thermal energy, in generating a gradient of negative entropy as its corollary, gives rise to “a self-sustaining system chemical system capable of Darwinian evolution.”

Let us further invite into our consideration the point that was likely an original impetus for NASA to generate such a definition: the ability to recognise the phenomenon of life in the event that it was not given to immediate apprehension. Likely the notion of identifying extraterrestrial life, as well as formulating a standard to determine the synthesis of artificial life, represent specific considerations in this respect. Let us inquire whether “the spontaneous organisation of molecules to dissipate thermal energy with greater efficiency and the correlative production of negative entropy” provides for such recognition. What about a “self-sustaining chemical system capable of Darwinian evolution?” In other words, could the above definitions convey the meaning of “life” to someone who had no concept of it? There is no way to answer this question other than to check what we mean when we say “life” and to see whether it matches essentially with these proposed definitions. If the answer is “no,” then we must either conclude (1) that the definitions fail or (2) that scientists mean something different when they use the word “life” than what people ordinarily mean when they use that word.

Empirical investigation confirms that the conceptions of life in terms of chemistry, physics, and Darwinism, which we delineated above, convey a meaning of “life” that is estranged from what people ordinarily mean when they use that word. Philosophical inquiry further exposes an insufficiency of such conceptions. For example, despite the fact that specific phenomena manifest under specific conditions, this does not usually justify one to conclude that the latter are the former’s cause. For instance, nobody supposes that clocks cause the time of day, nor that the time of day causes time in an astronomical reference frame. We might analogously wonder whether thermodynamics are causing anything. We might further wonder whether the laws of thermodynamics are causal powers at all, or if they are merely equations formulated and employed for their predictive and descriptive utility. Does it even make sense to think of a “physical law” as something with causal efficacy? It depends what “law” means. In the context of the physical sciences, laws are generalised mathematical descriptions based on observed facts that are subsequently universalised by extrapolation. Isaac Newton articulated this notion in the most expressively ex cathedra manner in the third axiom of his “rules of philosophy” in the 1713 edition of his Philosophiæ Naturalis Principia Mathematica. According to the regula tertia philosophandi:

Those qualities of bodies that cannot be intended and remitted [i.e., qualities that cannot be increased and diminished] and that belong to all bodies on which experiments can be made should be taken as qualities of all bodies universally.

By this axiom (the vagueness of its meaning notwithstanding), Newton meant to ground his methodological extrapolation of mathematical formulae, first derived as general descriptions of particular cases, to universal laws. For instance, Newton developed a formula to describe the phenomenon of falling bodies (e.g. the notorious apple) to his law of universal gravitation, elegantly expressed as the principle that every object attracts every other object in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. A “law” of this sort—like the laws of inertia that Newton also developed, as well the laws of thermodynamics, which where developed through the cooperation of many scientists over the seventeenth, eighteenth, and nineteenth centuries—is manifestly describing events, not causing them. “Law” in this case means “an abstract formula to describe concrete events.” Indeed, one might even say that the events cause the law. Though such a statement would stretch the meaning of “cause,” the claim would nevertheless be more accurate than its converse. Newton was well aware of this fact: in a letter from 1692, he wrote:

That one body may act upon another at a distance through a vacuum without the mediation of anything else, by and through which their action and force may be conveyed from one another, is to me so great an absurdity that, I believe, no man who has in philosophic matters a competent faculty of thinking could ever fall into it.

Furthermore, in the introduction to the 1713 edition of Principia, he stated very plainly:

I have not yet been able to discover the cause of these properties of gravity from phenomena and I feign no hypotheses (hypothesis non fingo!)…It is enough that gravity does really exist and acts according to the laws I have explained, and that it abundantly serves to account for all the motions of celestial bodies.

If we now inquire into our original question, it will be very clear that to postulate the the laws of thermodynamics as the cause of life is as a confusion of concepts. One must conclude, therefore, that thermodynamics fails to account for life, either in its nature or in its origin, and that if it appears to do so, this it does by substituting a factitious meaning for the word.

We may now question whether “a self-sustaining chemical system capable of Darwinian evolution” fares any better in an attempt to capture the meaning of “life.” It is interesting to note that, though evolution of species through natural selection has not been verified by the ordinary standards of empirical verification, advances in computational capacity do allow scientists to model hypothetical trajectories of Darwinian evolution. These models are certainly not living and yet they fulfil the second part of the definition above. The phrase “self-sustaining chemical system” is very vague, but any individual living creature that is familiar to us seems to fall short, since each one seems to depend on exchange with, and nourishment from a comprehensive ecosystem. Perhaps the solar system as a whole fulfils this criterion, but then one has again begun to mean by the word “life” something different than what is the normal meaning of that word. Finally, one can easily extrapolate from the present rate of technological advance to a not-so-distant future in which scientists will have created an artificial intelligence system that fulfils the stipulated definition of life in its entirety. This presents the paradoxical situation in which life as we know it does not meet the criteria of its own definition, while a synthetic system has come to easily fulfil them. This grotesque possibility hints at an implicit bias in our manner of conception, and an ineluctable problem in our conventional scientific methods. Namely, by demanding a definition be formulated in quantitative terms, we risk overlooking the very phenomenon we set out to define, and in our apparent solutions we have simply succeeded in having defined our own definition. Galileo Galilei’s paternal grandfather, a shepherd, used to count his sheep with pebbles but then forgot about the sheep. With such facility do we see the foolishness of others; with such difficulty do we acknowledge the same foolishness in ourselves. Thus, when questioned, old Galilei replied that he was actually using his sheep to count his rocks, and then ingeniously cut out the middle term, and that the sheep were really not intrinsically different from rocks in any case and only extrinsically so.

If we return in our consideration to the question of life, we must conclude that the approach of the scientists above has either failed in its attempt at definition, or simply stipulated a novel definition for the word and is therefore defining something different than what we usually mean by “life.” To suppose otherwise is to mistake the necessary conditions for a phenomenon with sufficient ones for it, or to conflate an entity with the medium in which it appears. No reasonable person, for instance, expects to define Hamlet by appealing to the laws of Elizabethan English grammar. Neither do they expect to have done this after a description of its typeface, no matter how exhaustive. Our insufficiency in respect to defining life invites us to reconceive our methods; our failure is a slughorn that calls us to rise to a new challenge.

So far in our inquiry, we have weighed various conceptions of life that conventional science provides and concluded that they fall short by (1) mistaking the medium in, by, or through which a phenomenon appears for that phenomenon itself and by (2) mistaking an essence for an accident, or a subject for its predicates. In a future piece, we will develop the second point and attempt to articulate the meaning of “life” outside of its technical connotation within the field of quantitative science. Specifically, we will explore the possibility of understanding life through the notion of “immanent causation.”

Works cited, thanks to:

What Is Life—and How Do We Search for It in Other Worlds?
Chris P McKay PLoS Biology, 2004



Erwin Schrödinger (1944), “What Is Life? : The Physical Aspect of the Living Cell”. Based on lectures delivered under the auspices of the Dublin Institute for Advanced Studies at Trinity College, Dublin, in February 1943.


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