The Physical Basis of Mind. George Henry Lewes
The laws of Physics and Chemistry formulate abstract expressions of phenomena, wherever and whenever these appear, without reference to the modes of production; and in this sense the movement of a limb is no less a case of Dynamics than the movement of a pulley—the decomposition of a tissue is a case of Chemistry no less than the decomposition of a carbonate; the electromotor phenomena observed in muscle are as purely physical as those observed in a telegraph. But when a biologist has to explain the movements of the limbs, or the decompositions of tissues, he has to deal with the phenomena and their modes of production, he has a particular group before him, and must leave out nothing that is characteristic of it. The movements of the pulley do not depend on Contractility and Sensibility, which in turn depend on Nutrition. The decomposition of the carbonate does not depend on conditions resembling those of a living tissue. Vaucanson’s duck was surprisingly like a living duck in many of its movements; but in none of its actions was there any real similarity to the actions of a bird, because the machine was unlike an organism in action. The antithesis of mechanism and organism will be treated of in § 78.
23. We conclude, then, that defining physical phenomena as the movements which take place without change of structure, and chemical phenomena as the movements with change of structure, although both classes may be said to take place in the organism, and to be the primary conditions on which organic phenomena depend, they do not embrace the whole of the conditions, nor are the sciences which formulate them capable of formulating either the special phenomena characteristic of organisms or their special modes of production. The biologist will employ chemical and physical analysis as an essential part of his method; but he will always rectify what is artificial in this procedure, by subordinating the laws of Physics and Chemistry to the laws of Biology revealed in the synthetic observation of the organism as a whole. The rectification, here insisted on, will be recognized as peculiarly urgent in Psychology, which has greatly suffered from the misdirection of Analysis.
24. No one will misunderstand this specialization of Biology to mean a separation of Life from the series of objective phenomena, and the introduction of a new entity; the specialization points to a Mode of Existence. All classifications are artifices, but they have their objective grounds; the ground of difference on which Biology is separated from Chemistry and Physics, though all three may be merged in a common identity, is such as to justify the term radical. A vital process is no more to be considered physico-chemical, because physico-chemical conditions are presupposed in it, than a feeling is to be considered a nutritive process, because Nutrition is presupposed in all Feeling. Organic substances have been made by chemists, and inorganic “cells” have also been made; but these substances were not organized, these “cells” would not live. The germ-cell is the workshop of generation, the secreting-cell the workshop of secretion, the muscle-cell the workshop of contraction. What is required over and above organic substances and cell-forms, is that special state called organization. See § 49.
Those who contemplate the manifestations without also taking into account their modes of production may see nothing but physico-chemical facts in vital facts. It is by a similar limitation of the point of view that Vitality is often confounded with Movement, and portions of organic matter are said to live, simply on the evidence of their movements.7
CHAPTER II.
DEFINITIONS OF LIFE.
25. Biology, the science of Life, being thus assigned its place in the hierarchy of objective laws, we now proceed to consider what the term Life symbolizes.
By a large preliminary simplification, Life may be defined as the mode of existence of an organism in relation to its medium. To render this of any value, however, a clear conception of the organism is first indispensable; and this must be preceded by an examination of the various attempts to define life in anticipation of such a clear conception.
26. Every phenomenon, or group of phenomena, may be viewed under two aspects—the statical, which considers the conditions of existence; and the dynamical, which considers these conditions in their resultant—in their action. The statical definition of Life will express the connexus of the properties of organized substance, all those conditions, of matter, form, and texture, and of relation to external forces, on which the organism depends. These various conditions, condensed into a single symbol, constitute Vitality or Vital Force, and are hence taken as the Cause of vital phenomena. The dynamical definition will express the connexus of Functions and Faculties of the organism, which are the statical properties of organized substance in action, under definite relations.
It is obvious that the term Life must vary with the varying significates it condenses—every variation in the complexity of the organism will bring a corresponding fulness in the signification of the term. The life of a plant is less significant than the life of an animal; and the life of a mollusc less than that of a fish. But not only is the term one of varying significance, it is always an abstract term which drops out of sight particular concrete differences, registering only the universal resemblances.
* * * * *
27. It would be a profitless labor to search out, and a wearisome infliction to set down, the various definitions which have been proposed and accepted; but certain characteristic examples may be selected. All that I am acquainted with belong to two classes: 1°, the meta-physiological hypothesis of an extra-organic agent, animating lifeless matter by unknown powers; 2°, the physiological hypothesis which seeks the cause of the phenomena (i.e. the conditions) within the organism itself—a group of conditions akin to those manifested elsewhere, but differently combined. The first hypotheses are known under the names of Animism and Vitalism—more commonly the latter. The second are known as Organicism and Materialism—but the latter term only applies to some of the definitions.
28. Under Vitalism are included all the hypotheses of a soul, a spirit, an archæus, a vital principle, a vital force, a nisus formativus, a plan or divine idea, which have from time to time represented the metaphysical stage of Biology. The characteristic of that stage is the personification of a mystery, accompanied by the persuasion that to name a mystery is to explain it. In all sciences when processes are imperfectly observed, the theory of the processes (which is a systematic survey of the available evidence marshalled in the order of causal dependence) is supplemented by hypothesis, which fills up with a guess the gap left by observation. The difference between the metaphysical and the positive stages of a science lies in the kind of guess thus introduced to supplement theory, and the degree of reliance accorded to it. I have more than once insisted on the scientific canon that “to be valid, an explanation must be expressed in terms of phenomena already observed”; now it is quite clear that most of the extra-organic hypotheses do not fulfil this condition; no one having ever observed a spirit, an archæus, or a vital principle; but only imagined these agents to explain the facts observed. As an example of the difference, and a proof that the value of an hypothesis does not rest on the facility with which it connects observations, and seems to explain them, take the three hypotheses of animal spirits, nervous fluid, and electricity, by which neural processes have been explained. The animal spirits are imaginary; the nervous fluid is without a basis in observation, no evidence of such a fluid having been detected; but electricity (or, speaking rigorously, the movements classed as electrical), although not proved to be the agent in nerve-action, is proved to exist in nerves as elsewhere, and its modes of operation are verifiable. It, therefore, and it alone of the three hypotheses, is in conformity with the scientific canon. It may not, on full investigation, meet all requirements; it may be rejected as imperfect; but it is the kind of guess which scientific theory demands.
The second difference noticeable between the metaphysical and the positive stages is the degree of reliance accorded to hypothesis; which is very much the same as that noticeable in the uncritical and critical attitudes of untrained and trained intellects. The one accepts a guess as if it were a proof; is fascinated by the facility of linking together isolated observations, and,