Regarding Definitions

Jabberwock (Lotka, 1925)
Attempts a definitions of “life”, from a physicochemical point of view, and or efforts to discern a “life/non-life” divide, via similar means, according to Alfred Lotka (1925), as elaborated on in his erudite chapter “Regarding Definitions”, is but a hunt for the Jabberwock, the fictional monster of the 1871 nonsense poem “Jabberwocky” by Lewis Carol, which is made entirely of nonsense words. [2]
In famous publications, Regarding Definitions is the famous opening chapter to Austrian-born American physical chemist Alfred Lotka’s 1925 Elements Physical Biology, wherein he grapples with the difficulties of attempting to define ‘life’ as physics and chemistry see "things", in which he topples all the standing definitions of life, models of life, and theories of life as lacking foundation; at the end of which he nearly states outright, somewhat prophetically, that the future will, in all likelihood, see the term "life" jettisoned from the corpus of exact sciences, the primary reason being that scientific searches for the origin of life is akin to a hunt for the Jabberwock, i.e. an attempt to scientifically explain a nonsense word, therein resulting in "objectionable nonsense", as Einstein would say (see: Einstein-Murphy dialogue), when scientific assertions are made.

Overview
Lotka, in his note 18, states the following ripe discernment, in respect to "systems" defined energetically, e.g. heated by sunlight:

“It should be observed that nothing has been said of life in describing the system. The system may or may not comprise living organisms, the argument remains the same. This suggests that a term, such as life, so vague that it defies definition, is perhaps not likely to play an important part in any exact argument; we may, indeed, find it wholly unnecessary. It may, in time, in the literature of exact science, meet with the fate of the word cause: a term of rare and at best incidental occurrence in records of exact investigations.”

Lotka, here, in pioneering fashion nearly reaches the “life disappears from the scene when physics and chemistry have entered” view (Sherrington, 1938), and nearly the “we should abandon the word alive” position (Crick, 1966), and close to the “defunct theory of life” (Thims, 2009) and more recent “life does not exist” (Rogers, 2010; Jabr, 2013) positions. In the end, he concludes that searching for the life/non-life distinction is but a game of “hunting for the Jabberwock”. [2]

Not able to jettison the term “life” as defunct, and or suggest terminology reform (see: life terminology upgrades), though he does hint at this (e.g. the function quantity ½mv ² is called “kinetic energy’, a universal term), likely owing to his early time period, he ends with: “we shall, wherever convenient, continue to employ the terms life, living organism, merely as a matter of convenience.” Jumping ahead a century, it is has become no longer convenient, in fact inconvenient, to retain the term “life”, e.g. in attempting to define fields of study such as “bio-thermodynamics” (see: biothermodynamics) or bio-physics (see: biophysics), or terms such as "bio-Gibbs free energy" (e.g. Mark Janes) or "bio-photon" (e.g. Zack Zwiebel), which, to use Lotka’s language, insert the Jabberwock, a fictional concept, into hard science (nonfiction subject).

Contents
The following is the full chapter: [1]

CHAPTER I
REGARDING DEFINITIONS

Truth comes out of error more readily than out of confusion.
Francis Bacon (1620), New Instrument of Science (§2:Aphorism 20) (Ѻ)

A definition is a purely arbitrary thing. If I choose to define a triangle as a plane figure bounded by four sides and having four angles; and if, also, I define a quadrilateral as a plane figure bounded by three sides and having three angles, I shall run into no logical conflicts; my geometry need in no wise depart from that of Euclid; I shall need to make no changes in existing works on geometry, beyond that of substituting throughout the word triangle for the word quadrilateral, and vice versa.

But while a definition is in this sense, from the point of view of logic, a purely arbitrary thing, while my definition of a triangle as a four-sided figure may be ‘admissible’, it is by no means expedient.

Thus the definition of terms, which naturally forms one of the first steps in the systematic treatment of any subject, may present no particular problems of logic, but it does present certain problems of expediency.

In the geometrical example cited, the unusual definitions given, though quite permissible, are inexpedient for simple etymological reasons. Such a choice of terms would be misleading, and, instead of assisting the memory, would impose upon it an unnecessary burden. In this case the application of the principle of expediency is obvious to the point of being grotesque, the example having purposely been chosen to illustrate the principle in drastic fashion.

But the framing of definitions at times involves more subtle considerations of expediency, so subtle in fact, that they may be overlooked, or misunderstood, and a problem which is, in truth, a problem of definition, falsely masquerades as a problem of fact. Certain pseudo-problems of science have owed their origin to a failure to realize this circumstance. [N1]

The writer of the book of Genesis shows good judgment. Our legendary forebear, the originator of the first biological system of nomenclature, sees each creature first, and thereupon names it. We have not always been equally wise. Sometimes we have tried to invert the method; we have found or made a name, and then gaily set forth on an expedition to discover the thing that should answer to that name; we have hunted the Jabberwock. Forgetful of the wisdom of Mephistopheles:

“Derm eben wo Gedanken fehlen / Da stellt ein Wort zur rechten Zeit sich ein”
[For precisely where thought missing / Since provides a word at the right time, a]

we have given way to an inherent bias of the human , mind described in characteristic fashion by H.G. Wells: [N2]

“When we have a name we are predisposed and sometimes it is a very vicious predisposition to imagine forthwith something answering to the name If I say Wodget or Crump, you find yourself passing over the fact that these are nothings, .... and trying to think what sort of a thing a Wodget or a Crump may be. You find yourself insensibly, by subtle associations of sound and ideas, giving these blank terms attributes. [N3]”

So the biologist of the past generation, finding in his native vocabulary the words ‘animal’ and ‘plant’, forthwith proceeded in an effort to establish precise distinctions between animals and plants, never giving any thought, it would seem, to the fact that these names had already been parceled out generations ago, by ‘popular’ consent, by unscientific persons without any regard to fine distinctions. There is clearly, here, the tacit assumption that because two distinct words are found in the vocabulary, therefore two correspondingly distinct things exist in nature. In point of fact, we know well enough (though we may not at all times have this knowledge clearly in the focus of our consciousness) that in nature many things form finely graded series, with extremes at the two ends, extremes to which our vocabulary has lent more or less definitely associated names, but with no definite line of demarcation between. Examples of this are innumerable. We speak of objects as being red, orange, yellow, green, blue, violet, etc. There is nothing in nature to correspond to such staccato classification of colors: the visible spectrum runs continuously from a wavelength of about 8x10^-4 mm (extreme red) to about 4X10^-4 mm (extreme violet). Cases therefore must necessarily arise when we are in doubt whether to call a thing blue, or green, for example; and such doubt can be resolved, if at all, only by arbitrary definition. The question is not ‘what is green, and what is blue’, but, at best, ‘what shall we agree to call green, and what blue.’

It lies in the nature of the mechanism by which we enter into possession of our knowledge, that problems of definition of this kind arise. We are equipped with two separate and distinct senses, the one responding to electromagnetic waves ranging from about 4x10^-4 to 8x10^-4 mm, light waves; the other to somewhat longer waves otherwise of the same character, heat waves. Accordingly we have two separate terms in our language ‘light’ and ‘heat’, to denote two phenomena which, objectively considered, are not separated by any line of division, but merge into one another by gradual transition. Here the question might be raised whether an electromagnetic wave of a length of 9 x 10^-4 mm is a light wave or a heat wave. The answer is obvious: Call it what you please, it is merely a question of arbitrary definition. We must beware of:

“That false secondary power by which we multiply distinctions, then deem that our puny boundaries are things, that we perceive, and not that we have made.”
— Wordsworth (c.1820)

Definitions in Biology
The attempt to establish a rigorous distinction between ‘animals’ and ‘plants’ may be similarly regarded. Expediency demands that if these terms are appropriated for exact scientific use, their sense, when so used, shall, if possible, be reasonably near akin to the sense commonly associated with these words. The difficulties encountered in seeking to establish a satisfactory line of division between animals and plants were long regarded as difficulties in a problem of fact. It was thought that some biological principle must be sought which divided animals from plants.

The truth is, of course, that we may define "animals" and "plants" any way we please- as for instance by reserving the term, plant for an organism possessing cellulose' but whether such definition is ‘correct’ or ‘satisfactory’ is not a question of biological fact, it is a question of expediency. It is not a question whether there is any definable difference between animals as a class and plants as a class, nor what this difference is, but whether it is expedient to retain for purposes of strict scientific classification the popular terms ‘animals’ and ‘plants’, which were not originally founded upon any rigorous examination of facts; and if so, where we should, by definition, draw the line of separation.

When the problem is viewed in this way the difficulty of distinguishing between animals and plants vanishes. In the case of the higher forms of life it is easy to establish biological distinctions that do not conflict with the popularly drawn lines of division. In the case of certain lowly forms of life popular distinctions cannot exist, since these forms are not known to the public except through biological publications. And the biological line of demarcation we can, by definition, draw arbitrarily where we choose, or, better perhaps, we may say that the terms ‘animal’, ‘plant’, do not correspond to any fundamental objective distinction and, though conveniently applied to certain common forms of living matter, are entirely unnecessary [N4] and only introduce difficulties of definition and classification when applied to certain simple organisms. What difference does it make whether we call Volvox a plant or an animal? Whether it is a plant or an animal is merely a matter of definition, not a question of biological fact.

Somewhat similar remarks apply to the narrower divisions into which the biologist divides the world of living organisms. Disputes as to what constitutes a species are fruitless. ‘A species is a thing described as such.’ This is simply a matter of definition. If on grounds of expediency one definition is preferable to another, it may be well to urge its general adoption. But its adoption or rejection will neither add nor subtract one jot from our stock of ascertained facts.

It is necessary to guard against the error of disputing about mere words. Not always does this error strut about in such blatant form as in the example quoted by Fechner: S. Sachs, in a book published in 1850, takes the astronomers to task for their presumptuous speculations: ‘How do they know that the star they call Uranus is Uranus?’

If anyone should think that in our day it is no longer necessary to guard against errors of this kind (though less gross, perhaps), let him consider such a question as this: Is not the perennial debate between vitalism and mechanism a quibble about words? Is not the whole situation summed up accurately in the words of L. J. Briggs: “The mechanism of plant processes not at present explainable on a physico-chemical basis would be termed by the vitalistic school ‘vital’, by the physico-chemical school ‘unknown’?” [N5]

And in searching for the essential characteristics of life, those that should finally and conclusively distinguish the living from the non-living, are we not just searching for the thing in nature that should correspond to a word in our vocabulary? Are we not hunting the Jabberwock?
Animate forms 3
Lotka, in his §:Definitions of Life (see: definitions of life), refutes Herbert Spencer’s definition of life, as: “The continuous adjustment of internal relations to external relations”, by pointing out that this same definition holds for the mechanical operation of the windmill.

Definitions of Life
The difficulty of giving a precise meaning to the word life has been realized probably by everyone who has ever seriously attempted a definition. Herbert Spencer remarks:

“Classifications are subjective concepts, which have no absolute demarcations in nature corresponding to them. Consequently, when we attempt to define anything complex we can scarcely ever avoid including more than we intended, or leaving out something that should be taken in. Thus it happens that on seeking a definition of life, we have great difficulty in finding one that is neither more nor less than sufficient.”

Nevertheless he proceeds to establish his definition of life: “The continuous adjustment of internal relations to external relations.” [N6] It cannot be said that Spencer has been very happy in this choice of a definition or that he has been at all successful in avoiding the very pitfalls which he himself so clearly points out. For obviously many purely mechanical systems fall under this definition. It would, for example, include a windmill provided with a device automatically turning its arms into the most favorable plane according to the direction of the wind. [N7] Indeed, in a sense it is true of every physical system that it ‘adjusts its internal relations to external relations.’ For this statement simply implies that there is a tendency for the establishment of equilibrium between a selected portion of a physical system, and the remainder, the environment.

Thus, for example, if the system 2H2 + O2 is left to itself hi a suitable vessel at 1480°C [N8] and one atmosphere pressure, the ratio H2/H20 which we may term an ‘internal relation’ of the system, assumes the value 0.0002. If now the external conditions of temperature and pressure are changed to 2929°C and one atmosphere pressure, the internal relation H2 / H20 adjusts itself to the new external condition and acquires the value 0.11.

Biology (recursive)
Lotka points out that standard dictionary definitions, e.g. "life is ‘the state of living", as well as most scholarly definitions, e.g. Dastre, following Claude Bernard: ‘the sum total of the phenomena common to all living beings’, are the same character as Sidney Smith's definition of an Archdeacon as ‘a person who performs archidiaconal functions’, i.e. circular.
With better judgment than Herbert Spencer, Sir Edward Schafer frankly evades the definition of life. He remarks: [N9]

“The ordinary dictionary definition of life is ‘the state of living’. Dastre, following Claude Bernard, defines it as ‘the sum total of the phenomena common to all living beings.’ Both these definitions are, however, of the same character as Sidney Smith's definition of an Archdeacon as ‘a person who performs archidiaconal functions.’ I am not myself proposing to grapple with a task that has proved too great for the intellectual giants of philosophy, and I have the less inclination to do so because recent advances in knowledge have suggested the probability that the dividing line between animate and inanimate matter is less sharp than it has hitherto been regarded, so that the difficulty of finding an inclusive definition is correspondingly increased.”

It is, indeed, an elementary historical fact that, as knowledge has advanced, the cope embraced in the term ‘vital’ processes has continually decreased, since Wohler took the first cut out of it in 1828 by the synthesis of a ‘vital product’ (urea) in the laboratory; and the field of known physico-chemical processes going on in living organisms has correspondingly increased. For the rest, the most uncompromising vitalist does not deny that some, at least, of the processes going on in living matter re physico-chemical. Even so fundamentally biological a process as the stimulation of n ovum to development we have learnt to effect by purely physical means.

Alleged Characteristics of Living Matter
On the other hand some of the features commonly ascribed to living matter as its peculiar and characteristic attributes seem Irrelevant to the point of triviality. This remark applies particularly to the distinction sometimes claimed for living matter, that it grows ‘from within’, as distinguished from crystals, which, in a suitable mother liquor, ‘grow from without’. There may or may not be many and profound differences between a bacterial colony growing in a culture medium, on the one hand, and on the other hand a mass of crystals growing in a supersaturated solution. But whether the growth takes place from within or without is merely an accident of structure. If a droplet of chloroform is brought near to a glass particle coated with shellac, the drop flows around the particle, engulfs it, absorbs the shellac coating and finally rejects the ‘undigested’ glass particle. [N10] The droplet thus grows ‘from within’.

In point of fact ‘growth from within’ is the rule and not the exception in chemical systems. For what do we mean by growth? We mean the increase of the mass of one component of a system at the expense of another. It is precisely the same thing as that which occupies the center of attention of the physical chemist, though he does not ordinarily call it growth. In fact, he does not find it necessary to give it any particular name, for, being accustomed to the use of mathematical methods and symbols, he simply writes it dm/dt, rate of increase of mass with time, or, more often, d/dt (m/v), rate of increase of concentration (mass/volume) with time. And in homogenous systems, at least, which (on account of their comparative ease of theoretical and experimental treatment) figure prominently in the physical chemistry of today, growth is necessarily from within.

Some writers (Jacques Loeb, The Organism as a Whole, 1916, p. 28) have seen a characteristic feature, peculiar to living organisms, as distinguished, for example from crystals growing out of a solution, in the fact that the latter grow by a physical process, the former by chemical processes. Leaving aside the question as to whether there exists any fundamental distinction between physical and chemical processes, at most the point to which attention is drawn by these authors would class living organisms with chemical, as distinguished from physical systems, but would furnish no basis whatever for separating organisms in a class by themselves from other chemical systems. This is not saying that they are not in a class by them- selves, but only that the distinction suggested fails in effect.

It has similarly been urged, as a distinction between the growth of a crystal and that of an organism, that the former will grow only in a supersaturated solution of its own substance, while the latter ex- tracts from an unsaturated solution the substance needed for its anabolism.

This is really the same distinction in another form. It may distinguish the organism from the growing crystal, but leaves it m... one class with any chemically reacting system whatever, since in the case of the latter also there is ‘growth’, i.e., formation of one or more products of reaction, in a system which need not be physically supersaturated in the narrow sense in which the crystallizing solution is. In a wider sense [N11] the system may indeed be said to be super-saturated with regard to a chemical substance that is formed within it but in the same sense a system can probably be said to be supersaturated with regard to the substance of a bacterial colony growing therein.

Neither can we subscribe to the view set forth by J. Loeb (The Organism as a Whole, 1906, p. 29), that the synthesis of specific materials from simple compounds of non-specific character distinguishes living from non-living matter. In every chemical reaction specific materials are formed. In a mixture of hydrogen, chlorine, and nitrogen, the hydrogen and the chlorine unite, leaving the nitro- gen on one side unchanged. This is merely a brutally simple example of a universal fact. Chemical reaction is always selective. And if ‘complexity’ is to be made the characteristic of life processes, then the question immediately arises, what degree of complexity is required to place a given process in the category of life processes?

Reproduction
Another characteristic that has been cited by some as exclusively peculiar to living organisms is the power of reproducing their kind. ‘How, says Driesch in effect, can a mechanism provide for its own reconstitution? No machine known to us is able to construct another like itself, nor can it repair its own parts.’ [N12]

Undue emphasis on this alleged distinction between living and non- living machines seems ill advised, for two reasons. In the first place, though it may be true that no man-made engine exists that performs the functions of self-repair and self-reproduction, no one has ever attempted, so far as I know, to demonstrate that no such engine can be built. Anyone who should be disposed to regard this objection as specious should reflect for a moment on the amazing development in technical arts within the last thirty or forty years. Half a century ago one might with equal justice have pronounced flight a fundamental, essentially biological characteristic of birds, incapable of duplication by man-made engines.

But in another, perhaps more significant respect, we must regard as misplaced the emphasis sometimes laid on the power of reproduction in organisms, and its absence in human artefacts. It is based on an exaggerated conception of the part played by the parent in the ‘making’ of the offspring. This probably has its origin in the instance of reproduction that to us is naturally of supreme interest, the reproduction of man. As a mammal, the young human organism grows within the parent body, and seems to us to be in some way ‘fashioned’ by the parent; this conception must be at the basis of the alleged distinction between organic reproduction and the incapacity of non-living engines to reproduce their kind, for without such conception the comparison would lack all parallel. Now, in point of fact, we need but call to mind the familiar hatching of a chick to realize that the part necessarily played by the parent in the formation of the young individual is really very restricted. The process in this case goes on, for the most part, in complete isolation from the parent. [N13]

As for the initiation of cell division of the ovum, we now know that, in some cases at least, this can be effected by ordinary physical means.

Recent development in experimental embryology suggest a more rational view of this process of self-reproduction of the living engine, a view which strips it of at least some of its mystery, and which certainly takes from it any force it might otherwise have had as a basis for distinction between living and non-living matter. If, after the first division of the ovum of a frog, the two cells are separated, each will under suitable conditions develop into a separate and complete, normal organism. These two organisms A and B are, in fact twin brothers or sisters. No one would for a moment entertain the thought that in this case A reproduces B, or vice versa. Now suppose that in some way, after the first division, A alone grows into a complete mature organism, while the single cell B remains attached to it, say for six months. At the end of this time it is separated, and stimulated to start its growth into a frog. We would ordinarily describe this state of affairs by saying that A reproduced B as offspring, that B was the child of A. In point of fact it is merely a delayed twin brother or sister of its elder brother or sister A. u A had little or nothing to do with the production of B; the latter grew, very much in the same way as A grew in its own time. That nature has evolved, in surviving races, this method of delayed development, so as to stretch out the totality of living organisms in a long chain, a succession in tune, is of course a fact of most fundamental importance, the significance of which will deserve our profound contemplation. One of its consequences has been to render possible a practically infinite number of organisms, built from a finite and quite restricted amount of matter, the same substance being used over and over again, for it is literally true that we live on our forefathers. Had all these organisms sought to grow simultaneously, their career would have been topped by lack of material.

If anyone should object that these reflections leave out of account entirely the role of sex in reproduction, with all the complex phenomena of the fusion of gametes, the mingling of chromosomes, and biparental inheritance, the obvious reply is that these phenomena are now known to be less fundamental than they formerly appeared; that reproduction of an organism can very well take place without them; and that therefore they may at most serve to distinguish certain forms of life from non-living matter, but they cannot possibly be made the basis of a distinction between living matter in general and that which we commonly describe as non-living.

Vital Force
If we have cause to hesitate in defining life, still more is it the part of wisdom to be very conservative in the coming and use of such phrases as ‘vital force’, ‘nerve energy’, and the like. Shall we not do well to follow the biblical example, and wait, to name the animal, until it is physically present to our senses? Or, to pass from legend to the world of scientific fact, let us borrow, if we can, the method of the physicist: He discovers that a quantity ½mv ² possesses certain important properties. Then, he proceeds to name it: energy, in particular, kinetic energy. But biologists have been disposed sometimes to adopt the reverse procedure: they have named a vital force, a nerve energy, a mental energy, and what not, and now they entertain the pious hope that in due time they may discover these ‘things’. That there is something radically at fault with such terms is evident from the fact that forces and energy are magnitudes, and ‘to define a magnitude and to say how it is measured are one and the same thing.’ [N15] But who has ever told us how to measure vital force [N16] and such like?

Physical Chemistry of Structured Systems
In the physical chemistry of today structure, that is to say, geometrical configuration, plays a subordinate role. For obvious reasons the theory of chemical reaction in homogeneous, or in heterogeneous systems of comparatively simple form, is more approachable than that of systems which possess intricate structure, resulting in complicated mechanical interactions of their parts, in accompaniment of chemical reaction. In technical practice, too, reactions in homogeneous systems (solution, gas) are common, and where there is heterogeneous structure, this is usually of a form very simple as compared with the complex biological structures.

But this comparative absence, from physico-chemical discussion, of reference to structure, to geometrical features, is not due to any inherent characteristic property of chemical systems, as contrasted with the structurally complex organic systems: the reason for the simplicity is to be found in ourselves. It is not a physical phenomenon of the thing observed, but a psychological phenomenon in the observer. Physical chemistry is still a comparatively young science, and naturally the simpler phenomena have been sought out for first attention. This is not because complex physico-chemical structures do not exist, nor even because they are unimportant. On the contrary, it is to be expected that the future will bring important developments in this direction, as followed, for example by Sir William Bayliss in his work Interfacial Forces in Physiology.

The rate of formation, the rate of growth, of a chemical substance, is a definite function of its environment. In a structureless system the nature and state of this environment is defined in comparatively simple terms (e.g. by stating the concentration of each of the reacting substances).

But in a system possessing structure, the environment of a given portion of the system depends on the structure, the topography of the system, which, in general, will be variable with the time. In particular, the structure may be such that a given substance or complex of substances carries its own immediate environment around with it. The rate of formation (growth) of that substance will then depend largely upon the mechanical properties of those portions of the system which accompany this substance or complex in its travels through the system.

The complete discussion of a system of this kind may well fall outside the scope of present day physical chemistry, not because it is inherently foreign to that branch of science, but because no case of this kind, sufficiently simple to invite discussion on a mathematical and physico-chemical basis, has clearly presented itself. [N17]

Yet there is absolutely nothing in such a case that in principle places it outside the pale of physico-chemical science. It is largely as the result of intentional selection of simple conditions that the systems with which the chemist ordinarily deals (outside of biological chemistry) are comparatively structureless.

We can, in fact, even now lay down certain general observations with regard to structured physico-chemical systems.

Let us consider a system of this kind in which local conditions are subject to variation from point to point and from instant to instant. We fix our attention on some one component which requires for its growth certain definite conditions of its immediate environment. If this component is associated with a structure whose geometrical and mechanical properties secure and maintain for it a comparatively constant suitable environment amid the changing conditions of the system, then that component will grow.

Furthermore, the several components will compete with greater or less success for the material available for their growth, in proportion as their structure is more or less perfectly adapted to secure and maintain for them a suitable environment.

The chemical dynamics of such a system, that is to say, the laws governing the distribution of matter among its several components, may evidently assume a fundamentally different character from that to which we are accustomed from our study of ordinary structureless systems. For in these latter the arrangement and rearrangement of matter within the system depends chiefly on chemical coefficients
(affinity coefficients), and scarcely at all on geometrical features. In structured systems, on the other hand, there is the possibility that geometrical and mechanical features may play the dominant role. This possibility will present itself particularly in those systems which receive a continuous or periodic supply of free energy, for instance in the form of illumination. Here the advantage will go to those structures that are adapted to direct available energy into such channels as lead to the maintenance of the environment required for their growth. [N18] But a little reflection shows that this is precisely the principle which governs survival in the struggle for existence among living organisms. Hence we may say:

The laws of the chemical dynamics of a structured system of the kind described will be precisely those laws, or at least a very important section of those laws, which govern the evolution of a system comprising living organisms.

For it is precisely structured systems of the kind considered above that are presented to us in living organisms growing in an environment’.

Application to Biology
The several organisms that make up the earth's living population, together with their environment, constitute one system, [N19] which receives a daily supply of available energy from the sun.

Each Individual is composed of various chemical substances assembled into a definite structure and capable of growth, i.e., of accretion out of the environment by chemical reaction—provided a suitable medium or environment is offered.

Moreover, each mobile organism carries with it a travelling environment, suitable for the growth of its substance. It maintains this environment by virtue of the peculiar mechanical properties associated with its structure, whereby it is enabled to turn to this use, directly or indirectly, the available energy of the sun's light. And while the travelling environment may not be absolutely constant, it is more nearly so than the more remote portions of the system, and keeps within such limits of variation as are compatible with the survival of the organism or its species. A concrete illustration may help to make this point clear. Many aquatic forms of life are constantly bathed in a saline solution sea water. Their body fluids are accordingly in equilibrium with this environment. Variations in the salinity of their environment, if they exceed certain comparatively narrow bounds, are apt to be fatal to such organisms.

The higher organisms have made themselves (largely) independent of their immediate environment. Their tissues are bathed from within by a fluid (the blood) which they carry around with them, a sort of ‘internal environment’. [N20]

The degree of perfection with which this constancy of the internal or traveling environment, independently of the external environment, is developed, increases as we ascend the biologic scale. This is lucidly set forth, for example, by Claude Bernard:[N 21]

“Chez tous les etres vivants le milieu interieur qui est un produit de l’organisme, conserve les rapports necessaires d’echange avec le milieu exterieur; mais
a mesure que l’organisme devient plus parf ait, le milieu organique se specifie et
s’isole en quelque sorte de plus en plus du milieu ambiant.”

It is the peculiar structure and the mechanical properties of the organism that enable it to secure and maintain the required environment (including the milieu interior). The higher animals, in particular, are provided with an intricate apparatus, comprising many members, for securing food (internal environment) as well as for warding off hostile influences.

The increasing independence, as we ascend the biological; ~ jale, which the organism displays toward its more remote environment, is thus accompanied by a parallel increase in the perfection of the apparatus by which this independence is earned. Here again we may quote Claude Bernard: [N22]
“A mesure que l’on s’eleve dans l’echelle des etres, ces appareils deviennent plus parfaits et plus eompliques; ils tendent a affranchir completement l’organisme des influences et des changements survenus dans le milieu exterieur. Chez les animaux invertebres, au contraire, cette independence vis-a-vis du milieu exterieur n’ est que relative.”

The Policy of Resignation: Its Parallel in Other Sciences
What-ever may be our ultimate conclusions, we may do well to adopt at least as a temporary expedient the policy of resignation; with Sir Edward Schafer we may abandon the attempt to define life. Perhaps, in doing this, we are following historical precedents: Geometers have had to resign themselves to the fact that Euclid's parallel axiom cannot be proved. But as the reward of this resignation came the new geometries of Bolyai, Lobatchewski and Riemann. Enlightened inventors have abandoned the attempt to build a perpetual motion machine; but again, resignation is rewarded with the recognition of a fundamental law, the law of conservation of energy. Physicists, following Einstein, have abandoned, for the time being at any rate, the attempt to determine experimentally the earth's absolute motion through space. The reward has been the theory of relativity, one of the greatest events in the history of science.

The whole development of science, especially in recent years, is a record of tearing down barriers between separate fields of knowledge and investigation. Little harm, and perhaps much gain, can come from a frank avowal that we are unable to state clearly the difference between living and non-living matter. This does not in any way commit us to the view that no such difference exists. For the present, then, we shall adopt the position that the problem is essentially one of definition. The question is not so much ‘what is life’, but rather, ‘what shall we agree to call life?’ And the answer, for the present at any rate, seems to be that it is immaterial how we define life; that the progress of science and our understanding of natural phenomena is quite independent of such a definition.

We shall, wherever convenient, continue to employ the terms life, living organism, merely as a matter of convenience. This use of the terms does not imply or resuppose any precise distinction between living and non-living matter; it merely rests upon the fact that in most cases ordinarily met there is essentially universal agreement as to whether a portion of matter is to be classed in the first or in the second category. We will adopt the policy of Sir William Bayliss:

“If asked to define life I should be inclined to do as Poinsot, the mathematician did, as related by Claude Bernard: ‘If anyone asked me to define time, I should reply: Do you know what it is that you speak of? If he said Yes, I should say, Very well, let us talk about it. If he said No, I should say, Very well, let us talk about something else’.”

The ideal definition is, undoubtedly, the quantitative definition, one that tells us how to measure the thing defined; or, at the least, one that furnishes a basis for the quantitative treatment of the subject to which it relates. We have already spoken of evolution. Most of what follows will relate directly or indirectly to evolution. It will be well here, while discussing definitions, to establish a definition, a conception, of evolution that shall, as far as may be, have the quantitative stamp.

Notes
N1. On the other hand, some very fundamental advances of science are, upon critical examination, found to rest essentially upon the establishment of a judicious definition. A notable instance of this is the enunciation of the principle of the survival of the fittest, which is essentially of the nature of a definition, since the fit is that which survives. Regarding the epistemological significance of definitions compare: A. N. Whitehead and B. Russell, Principia Mathematica 1910, vol. 1, p. 12.
N2. Wells, H.G. (1908). First and Last Things (pg. 32). Publisher.
N3. Goethe, Johann. (c.1810). “Gewohnlich glaubt der Mensch, wenn er nur Worte / Es mtisse sich dabei auch etwas denken lassen.” (Direction Usually man believes when he only words/ It mtisse thereby evoke something) Publication.
N4. (a) Quote: “We are justified at present in not classifying viruses either with plants or animals.”
(b) Glaser, W.R. (1918) “Article”, Science, 48:301-302.
N5. (a) Briggs, J.L. (1917). “Article”, Journal of the Washington Academy of Science, Vol. 7, p. 89.
(b) Compare also: E. M. East, Mankind at the Crossroads, 1923, p. 21.
N6. Spencer, Herbert. (1867). Principles of Biology (§30). Publisher.
N7. (a) Compare the following: “No one has yet succeeded in formulating a cleancut definition of the limits of the reflex either at its lower or its higher extreme, and perhaps no one ever will; for the whole list of behavior types, from machines to men, probably form a closely graded series.”
(b) Herrick, C.J. (1910). “The Evolution of Intelligence and Its Organs”. Science, 31:18.
N8. Nernst, Walther. (1913). Theoretische Chemie (pg. 713). Publisher.
N9. Schaefer, Edward A. (1912). “Life, Its Origin, and Maintenance” (Ѻ), Presidential Address, Dundee Meeting of BAAS. Publisher.
N10. Clarification: “Let it be clearly understood that this illustration is here quoted, not as an example of life-like analogies in the world of non-living matter; nor as a veiled suggestion that such a drop of chloroform represents even a modest degree of success in the artificial imitation of life; nor yet again as an argument that the conduct of amoeba can today be fully accounted for on a physico- chemical basis; this example was cited merely to show that ‘growth from within’ cannot be claimed as a distinguishing characteristic of living matter. For further discussion of so-called simulacra vitae see McClendon, Physical Chemistry of Vital Phenomena; Burns and Paton, Biophysics, 1921, p. 403.
N11. Note: namely in the sense that it is metastable, that is, its thermodynamic potential is not at a minimum.
N12. Warren, H.C. (1916). “Article”, Journal of Philosophy, Psychology, and Scientific Method, 13:36.
N13 Compare: E. G. Conklin, Heredity and Environment, 1918, pp. 99, 45, 109: “The hen does not produce the egg, but the egg produces the hen and also other eggs We know that the child comes from the germ cells and not from the highly differentiated bodies of the parents, and furthermore that these cells are not made by the parents' bodies but these cells have arisen by the division of antecedent germ cells
Parents da not transmit their characters to their offspring, but these germ cells in the course of long development give rise to adult characters similar to those of the parent.”
N14. The perhaps somewhat doubtfully authenticated cases of fetus in fetu, "those strange instances in which one might almost say that a man may be pregnant with his brother or sister," add a touch of realism to the discussion here presented. For further data on this singular subject see G. M. Gould and W. L. Pyle, Anomalies and Curiosities of Medicine, 1897, pp. 199 et seq. Compare also in this connection, the phenomenon of pedogenesis; see for example, G. H. Parker, Psyche, 1922, vol. 29, p. 127.
N15. Nature, September 25, 1922, p. 405.
N16. G. Bunge, in his Physiologic and Pathologic Chemistry, 1902, p. 1, re- marks : "I regard vital force as a convenient resting place where, to quote Kant, 'reason can repose on the pillow of obscure relations.'" Curiously enough this damning admission is made by an advocate of vitalism.
N17. Compare: W. M. Bayliss, Physiology, 1915, p. XI, “All that we are justified in stating is that, up to the present, no physico-chemical system has been met with having met with having the same properties as those known as vital; in other words, none have, as yet, been prepared of similar complexity and internal coordination.”
N18. It should be observed that nothing has been said of life in describing the system. The system may or may not comprise living organisms, the argument remains the same. This suggests that a term, such as life, so vague that it defies definition, is perhaps not likely to play an important part in any exact argument; -we may, indeed, find it wholly unnecessary. It may, in time, in the literature of exact science, meet with the fate of the word cause: a term of rare and at best incidental occurrence in records of exact investigations.
N19. This fact deserves emphasis. It is customary to discuss the ‘evolution of a species of organisms.' As we proceed we shall see many reasons why we should constantly take in view the evolution, as a whole, of the system [organism plus environment]. It may appear at first sight as if this should prove a more complicated problem than the consideration of the evolution of a part only of the system. But it will become apparent, as we proceed, that the physical laws governing evolution in all probability take on a simpler form when referred to the system as a whole than to any portion thereof. It is not so much the organism or the species that evolves, but the entire system, species and environment. The two are inseparable. "The organism, as Uexkull teaches us, must be studied, not as a congeries of anatomical and physiological abstraction, but as a piece of machinery, at work among external conditions," O.C. Glaser, Science, vol. 21, 1910, p. 303.
N20. "Etant donne que l'eau de mer a un contact si intime avec les organismes de la mer et que non seulement elle les entoure de ses flots, mais qu'elle traverse leurs branchies et impregne en partie les corps des invetebres, il semble assez justind de la placer dans la meme cateegorie que les autres liquides physiologiques." S. Palitzsch, Comptes Rendus de Carlsberg, vol. 10, part 1, 1911, p. 93. Compare also the following:
"Not only do the body fluids of the lower forms of marine life correspond exactly with sea water in their composition, but there are at least strong indications that the fluids of the highest animals are really descended from sea water .... the same substances are present in both cases, and in both cases sodium chloride largely predominates." L. J. Henderson, The Fitness of the Environment, 1913, pp. 187-188. See also ibid., pp. 116 and 153; H. F. Osborn, The Evolution and Origin of Life, 1917, p. 37 ; D'Arcy W. Thomp- son, Growth and Form, 1917, p. 127.
N21. Introduction a l’etude de la me'decine experimentelle, 1885, p. 110.
N22. Ibid.

References
1. Lotka, Alfred J. (1925). Elements of Physical Biology; Republished (Ѻ) as: Elements of Mathematical Biology, which includes: corrections from Lotka’s notes and a completed list of his publications (pdf) (Ѻ) (txt) (§1: Regarding Definitions, pgs. 3-19). Dover, 1956.
2. Jabberwocky – Wikipedia.

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