Does living activity require a principle beyond physical and chemical processes?

In considering under this head the vital laws, the first view which they offer, is the remarkable difference which distinguishes them from physical laws. The one constantly varying in their intenseness, energy, and development, often pass with rapidity from the lowest degree of prostration to the highest point of exaltation, accumulate and diminish in the organs alternately, and assume, from the influence of the slightest causes, a thousand different modifications. Sleep, watching, exercise, rest, digestion, hunger, the passions, and the action of surrounding bodies, &c. expose them at every instant to numerous revolutions. The others, on the contrary, fixed, invariable, and constantly the same at all times, are the source of a series of phenomena always uniform. Compare the vital faculty of feeling, to the physical faculty of attracting, you will see that the attraction is always in proportion to the mass of rough body in which it is observed, while the sensibility changes its proportion incessantly in the same organic part and in the same mass of matter. The invariability of the laws which govern physical phenomena, permits us to calculate all the sciences which are the object of them; while applied to the actions of life mathematics can offer no general rules.

But we have set forth the theoretical reasons which prevent us from likening the living being, a system closed off by nature, to the systems which our science isolates. These reasons have less force, we acknowledge, in the case of a rudimentary organism like the amoeba, which hardly evolves at all. But they acquire more when we consider a complex organism which goes through a regular cycle of transformations. The more duration marks the living being with its imprint, the more obviously the organism differs from a mere mechanism, over which duration glides without penetrating. And the demonstration has most force when it applies to the evolution of life as a whole, from its humblest origins to its highest forms, inasmuch as this evolution constitutes, through the unity and continuity of the animated matter which supports it, a single indivisible history. Thus viewed, the evolutionist hypothesis does not seem so closely akin to the mechanistic conception of life as it is generally supposed to be. Of this mechanistic conception we do not claim, of course, to furnish a mathematical and final refutation. But the refutation which we draw from the consideration of real time, and which is, in our opinion, the only refutation possible, becomes the more rigorous and cogent the more frankly the evolutionist hypothesis is assumed.

Can you imagine a very complicated machine, differing in the three dimensions of space, to be divided hundreds and hundreds of times and in spite of that to remain always the same whole ? You may reply that during the period of cell-divisions there is still no machine, that the machine is established only after all the divisions are complete. Good ; but what then constructs this machine in the definitive cells of our systems, say in the eggs ? Another sort of machine perhaps ? That could hardly be said to be of much use. Or that entelechy of which we have spoken ? Then you would recur to our first proof of vitalism and would burden entelechy with a specific performance, that is with the construction of the hypothetic machine which you are postulating in every single egg. But of course you would break the bounds of physics and chemistry even then. … We say it is a mere absurdity to assume that a complicated machine, typically different in the three dimensions of space, could be divided many many times, and in spite of that always be the whole : therefore there cannot exist any sort of machine as the starting-point and basis of development. Let us again apply the name entelechy to that which lies at the very beginning of all individual morphogenesis.

The contents of life from the cradle to the bier are wishes and hopes, efforts and struggles, and unfortunately also dis appointments and suffering. And this inner life should be amenable to a physico-chemical analysis? In spite of the gulf which separates us today from such an aim I believe that it is attainable. As long as a life phenomenon has not yet found a physico-chemical explanation it usually appears inexplicable. If the veil is once lifted we are always surprised that we did not guess from the first what was behind it. That in the case of our inner life a physico-chemical explana tion is not beyond the realm of possibility is proved by the fact that it is already possible for us to explain cases of simple mani festations of animal instinct and will on a physico-chemical basis; namely, the phenomena which I have discussed in former papers under the name of animal tropisms, As the most simple example we may mention the tendency of certain ani mals to fly or creep to the light. We are dealing in this case with the manifestation of an instinct or impulse which the animals cannot resist. It appears as if this blind instinct which these animals must follow, although it may cost them their life, might be explained by the same law of Bunsen and Roscoe, which explains the photochemical effects in inanimate nature.

Ici nous serons seulement physiologiste et à ce titre, nous ne pouvons nous placer ni dans le camp des vitalistes, ni dans celui des matérialistes. Nous nous séparons des vitalistes, parce que la force vitale, quel que soit le nom qu’on lui donne, ne saurait rien faire par elle-même, qu’elle ne peut agir qu’en empruntant le ministère des forces générales de la nature et qu'elle est incapable de se manifester en dehors d’elles. Nous nous séparons également des matérialistes; car, bien que les manifestations vitales restent placées directement sous l’influence de conditions physico-chimiques, ces conditions ne sauraient grouper, harmoniser les phénomènes dans l’ordre et la succession qu’ils affectent spécialement dans les êtres vivants.

In the first lecture I stated as clearly as I could the arguments in favour of the mechanistic theory of life, and the fatal objections which may be urged against vitalism or animism. The second lecture was devoted to criticism of the mechanistic theory. I endeavoured to show that the experimental evidence which has been brought forward in support of this theory will not bear critical examination, and that the popular idea that the progress of physiology is in the direction of confirming or supporting the mechanical conception of life is a complete illusion. I then proceeded to discuss, in the light of biological facts, whether by any possibility the mechanistic theory may not still be correct. The result of this discussion was that there is no such possibility. The physical and chemical conception of the world breaks down absolutely and hopelessly in connection with the phenomena of life, however useful it actually is in connection with inorganic phenomena. It is, therefore, nothing but a working hjrpothesis of limited useful application. … It was then shown that we do actually employ the funda- mental working conception of living organisms as such, and that with the help of this con- ception we can bring order and intelligibi- lity into biological investigation, and we are provided with a working hypothesis which is of the utmost practical value in biological work.