On the Fourfold Root of the Principle of Sufficient Reason, and On the Will in Nature · Arthur Schopenhauer
PHYSIOLOGY OF PLANTS.
The corroborations I am now about to bring forward of the phenomenon of the will in plants, proceed chiefly from French sources, from a nation whose tendencies are decidedly empirical and which is reluctant to go a step beyond what is immediately given. The informant moreover is Cuvier, whose rigid adherence to the purely empirical gave rise to the famous dispute between him and Geoffroy de St. Hilaire. So we must not be astonished if the language we meet with here is less decided than in the preceding German corroborations and if we find each concession made with cautious reserve. In his "Histoire des Progrès des Sciences Naturelles depuis 1789 jusqu'á ce jour,"[247] Cuvier says: "Plants have certain apparently spontaneous movements, which they show under certain circumstances and which at times so closely resemble those of animals, that a sort of feeling and _will_ might almost be attributed to plants on this account, especially by those who think they can perceive something of the same kind in the movements of the _inward_ parts of animals. Thus the tops of trees always have a vertical tendency, excepting when they incline towards the light. Their roots seek out good earth and moisture and, in order to attain these, deviate from the straight course. Yet these different tendencies cannot be explained by the influence of external causes, unless we also assume the existence of an inner natural disposition, susceptible of being roused, which differs from the mere mechanical force in inorganic bodies.... Decandolle made some remarkable experiments that proved to him the existence of a sort of habit in plants which may be overcome by artificial light, but only after a certain time. Plants that had been shut up in a cellar which was continually lit by lamps, did not on this account leave off closing in the evening and opening again in the morning for several days.
And there are other habits besides which plants are able to adopt and to abandon. Flowers that habitually close in wet weather, finish by remaining open if the wet weather lasts too long. When M. Desfontaines took a sensitive plant with him in his carriage, the jolting movement at first caused it to contract, but at last it expanded again as when in complete repose. Therefore even in these cases, light, moisture, &c., &c., only act in virtue of an inner disposition, which may be neutralized or modified by the continuation of that very activity itself; and the vital energy of plants, like that of animals, is subject to fatigue and exhaustion. The _hedysarum gyrans_ is singularly characterized by the movements of its leaves which continue day and night without needing any sort of stimulus. Surely, if any phenomenon can cause illusion and remind us of the voluntary movements of animals, it is this. Broussonet, Silvestre, Cels and Halle have fully described it, and have shown that the plant's action depends entirely upon its own healthy condition." [247] Vol. i. p. 245. 1826.
Again, in the third volume of the same work, p. 166 (1828), Cuvier says: "M. Dutrochet adds some physiological considerations to which his own experiments had led him, and which in his opinion prove that the movements of plants are _spontaneous_, _i.e._ that they depend upon an inner principle which immediately receives the influence of outer agencies. As he is however reluctant to admit that plants have feeling, he makes use of the word '_nervimotilité_.'"--Here I must observe, that when we come to examine it closely, what we think to ourselves in the conception of _spontaneity_, is in the end always the same thing as manifestation of will, with which spontaneity would therefore be simply synonymous. The only difference between them consists in the conception of spontaneity being derived from outer perception, while that of manifestation of will is drawn from our own consciousness.--I find a remarkable instance of the impetuous violence of this spontaneity, even in plants, in the following communication contained in the "Cheltenham Examiner:"[248] "Last Thursday four enormous mushrooms performed a heroic feat of a new kind, in one of our most crowded streets, by lifting up a huge block of stone in their strenuous effort to make their way into the visible world." [248] Repeated in the "Times" of June 2nd, 1841.
In the "Mém. de l'Acad. d. Sciences de l'année" (1821), Cuvier says[249]:--"For centuries botanists have been searching for the reason why in a seed which is germinating the root invariably grows downwards, while the stalk as invariably grows upwards, no matter what be the position in which the seed is placed. M. Dutrochet put some seeds into holes bored in the bottom of a vessel filled with damp mould, which he hung up to a beam in his room. Now, in this case, the stem might have been expected to grow downwards. Not at all: the roots found their way to the air below, and the stems were prolonged so as to traverse the damp mould until they reached its upper surface. According to M. Dutrochet, the direction in which plants grow, is determined by an inner principle and not at all by the attraction of the bodies towards which they direct themselves. A mistletoe seed that was fastened to the point of a perfectly moveable needle fixed on a peg, with a small plank placed near it, was induced to germinate. It soon began to send out shoots towards the plank, which it reached in five days without having communicated the slightest movement to the needle. The stems of onions and leeks with their bulbs, deposited in dark places, grow upwards, although more slowly than in light ones; they grow upwards even if placed in water: a fact which suffices to prove that neither light nor moisture determines the direction of their growth."--Still C. H. Schultz asserts[250] that he made seeds germinate in a dark box with holes bored in the bottom, and succeeded in inducing the plants to grow upside down, by means of a mirror fastened to the box, which reflected the sunlight.
F. J. Meyen has devoted a chapter, entitled "Of the movements and sensations of plants," to a full investigation of the subject now before us. In this he says[251]: "Not unfrequently potatoes, stored in deep, dark cellars, may be observed towards summer to shoot forth stems which invariably grow in the direction of the chinks through which the light comes into the cellar, and to continue thus growing until they at last reach the aperture which receives the light directly. In such cases potato-stalks have been known to reach a length of twenty feet; whereas under ordinary circumstances, even such as are most favourable to the growth of the potato, the stalk is seldom longer than from three to four feet. It is interesting to watch closely the course taken by a potato-stalk thus growing in darkness, in its endeavours to reach the light. It tries to do so by the shortest road, but not being firm enough to grow straight across through the air without support, it lets itself drop on to the floor, and thus creeps along the ground till it reaches the nearest wall, up which it then climbs." Even this botanist too is led by his facts to the following assertion (p. 576): "On observing the freedom of movement of _oscillatoria_ and other inferior plants, we may perhaps have no alternative but to attribute a species of _will_ to these beings."
1843. The result is, that in _pisum sativum_ (green pea), in _bryonia alba_ (wild bryony) and in _cucumis sativus_ (cucumber) the stems of those leaves which bear the tendrils, describe a very slow circular movement in the air, the time in which they complete an ellipsis varying from one to three hours according to temperature. By this movement they seek at random for solid bodies round which, when found, they twine their tendrils; these then support the plant, it being unable to stand by itself without help. That is, they do the same thing as the eyeless caterpillar, which when seeking a leaf describes circles in the air with the upper part of its body. Dutrochet contributes a good deal of information too concerning other movements in plants in this treatise: for instance, that _stylidium graminifolium_ in New Holland, has a column in the middle of its _corolla_ which bears the anthers and _stigma_ and alternately folds up and unfolds again. What Treviranus adduces is to the same effect:[253] "In _parnassia palustris_ and in _ruta graveolens_, the stamina incline one after the other, in _saxifraga tridactylites_ in pairs, towards the stigma, and erect themselves again in the same order."--Shortly before however, we read in Treviranus with reference to this subject: "Of all apparently voluntary movements of plants, the direction of their boughs and of the upper surface of their leaves towards the light and towards moist heat, and the twining movements of creepers round their supports, are the most universal. In this last phenomenon especially there is something which resembles animal movements. While growing, creepers, it is true, if left to themselves, describe circles with their tips and by this means reach an object near at hand. But it is no merely mechanical cause that induces them to adapt their growth to the form of the object they have thus reached.
The _cuscuta_ does not twine round every kind of support: for instance, limbs of animals, dead vegetable matter, metals and inorganic substances are not used for this purpose, but only living plants, and not even all kinds--not mosses, for instance--only those from which it can extract nourishment by its _papillæ_; and these attract it from a considerable distance."[254] The following special observation, communicated to the "Farmer's Magazine," and reproduced by the "Times" (13th July 1848) under the title "Vegetable Instinct," is however still more to the point: "If a basin of water be placed within six inches of a young pumpkin-stalk, or of a stem of the large garden pea, no matter on what side, the stalk will approach the basin during the night and it will be found next morning with one of its leaves floating on the water. This experiment may be renewed every night till the plant begins to fructify.--Even if its position be changed every day, a stick fixed upright within six inches of a young convolvulus is sure to be found by the plant. If, after having wound itself for a certain distance round the stick, it is unwound and wound round again in the opposite direction, it will return to its original position or lose its life in the endeavour to do so.
Nevertheless, if two such plants grow close to one another without having any stick near enough for them to cling to it, one of them will change the direction of its winding and they will twine round each other. Duhamel placed some Italian beans in a cylinder filled with moist earth; after a little while they began to germinate and naturally sent their _plumula_ upwards in the direction of the light and their _radicula_ downwards into the mould. After a few days the cylinder was turned round to the extent of a quarter of its circumference and the same process was repeated until it had been turned completely round. The beans were then removed from the earth, when it was found that both _plumula_ and _radicula_ had twisted at each turn that had been given, in order to adapt themselves to it, the one endeavouring to rise perpendicularly, the other to descend, so that they had formed a complete spiral. Yet, notwithstanding this natural tendency to descend, when the soil below is too dry, roots will grow upwards in order to reach any moist substance which may be lying higher than themselves." [252] These have been translated for the "Bibliothèque Britannique, Section des Sciences et Arts," vol. lii. [253] Treviranus, "Die Erscheinungen und Gesetze des Organischen Lebens" (Phenomena and Laws of Organic Life), vol. i. p. 173.
In the same periodical (1835, No. 981) is to be found a communication from Professor Daubeny, of Oxford (taken from the "Edinburgh New Philosophical Journal," April-July, 1835), in which he shows with certainty, by means of new and very careful experiments, that roots of plants have, at any rate to a certain degree, the power to make choice from those substances in the soil which present themselves to their surface.[255] [255] In this connection I may mention an analysis of an entirely different kind, given by the French Academician Babinet in an article in which he treats of the seasons on the planets. It is contained in the No. of the 15th January, 1856, of the "Revue des Deux Mondes," and I will give the chief substance of it here in translation. The object of it is to refer to its direct cause the well-known fact, that cereals only thrive in temperate climates. "If grain did not necessarily perish in winter, if it were perennial, it would not bear ears, and there would be no harvest. In the hotter portions of Africa, Asia and America, where no winter kills the grain, these plants grow like grass with us: they multiply by means of shoots, remain always green, and neither form ears nor run to seed. In cold climates, on the contrary, the organism of these plants seems by some inconceivable miracle to feel, as it were by anticipation, the necessity of passing through the seed-phase in order to escape dying off in the winter season" (_L'organisme de la plante_, par un inconcevable miracle, _semble préssentir la nécessité de passer par l'état de graine, pour ne pas périr complètement pendant la saison rigoureuse_).
In a similar way, districts which have a "droughty season,"--that is to say a season in which all plants are parched up with drought--"tropical countries, for instance Jamaica, produce grain; because there the plant, moved by the same organic presentiment (_par le même_ pressentiment organique), in order to multiply, hastens to bear seed at the approach of the season in which it would have to dry up." In the fact which this author describes as an inconceivable miracle, we recognise a manifestation of the plant's will in increased potency, since here it appears as the will of the species, and makes preparations for the future in a similar way to animal instinct, without being guided by knowledge of that future in doing so. Here we see plants in warmer climates dispensing with a complicated process to which a cold climate alone had obliged them. In similar instances animals do precisely the same thing, especially bees. Leroy in his admirable work "Lettres Philosophiques sur l'Intelligence des Animaux" (3rd letter, p. 231) relates, that some bees which had been taken to South America continued at first to gather honey as usual and to build their cells just as when they were at home; but that when they gradually became aware that plants blossom there all the year round, they left off working.
The animal world supplies a fact analogous to the above mentioned change in the mode of multiplying in cereals. This is the abnormal mode of propagation for which the _aphides_ have long been noted. The female _aphide_, as is well known, propagates for 10-12 generations without any pairing with the male, and by a variety of the ovoviviparous process. This goes on all summer; but in autumn the males appear, impregnation takes place, and eggs are laid as winter quarters for the whole species, since it is only in this shape that it is able to outlive the winter. (Add. to 3rd ed.) Finally I will not omit to observe, that even so early an authority as Plato[256] had attributed desires, ἐπιθυμίας, _i.e._ _will_, to plants. In my chief work,[257] however, I have entered into the doctrines of the Ancients on this point, and the chapter there which treats of this subject may on the whole serve to complete the present one. [256] Plat. "Tim." p. 403. Bip. [257] "Die Welt a. W. u. V." vol. ii. chap. 23.
The reluctance and reserve with which we see the authors here quoted make up their minds to acknowledge the will, which nevertheless undoubtedly manifests itself in plants, comes from their being still hampered by the old opinion, that consciousness is a requisite and condition of the will: now it is evident that plants have no consciousness. The thought never entered into the heads of these naturalists, that the will might be the _prius_ and therefore independent of the intellect, with which, as the _posterius_, consciousness first makes its appearance. As for knowledge or representation, plants have something merely analogous to it, a mere substitute for it; whereas they really have the will itself quite directly: for, as the thing in itself, it is the substratum of their phenomenal being as well as of every other. Taking a realistic view, starting accordingly from the objective, the matter might even be stated as follows: That which lives and moves in plant-nature and in the animal organism, when it has gradually enhanced itself in the scale of beings sufficiently for the light of knowledge to fall directly upon it, presents itself in this newly arising consciousness as _will_, and is here more immediately, consequently better, known than anywhere else.
This knowledge therefore must supply the key for the comprehension of all that is lower in the scale. For in this knowledge the thing in itself is no longer veiled by any other form than that of the most immediate apprehension. It is this immediate apprehension of one's own volition which has been called the inner sense. In itself the will is without apprehension, and remains so in the inorganic and vegetable kingdoms. Just as the world would remain in darkness, in spite of the sun, if there were no bodies to reflect its light; or as the mere vibration of a string can never become a sound without air or even without some sort of sounding-board: so likewise does the will first become conscious of itself when knowledge is added to it. Knowledge is, as it were, the sounding-board of the will, and consciousness the tone it produces. This becoming conscious of itself on the part of the will, was attributed to a supposed inner sense, because it is the first and most direct knowledge we have.
The various emotions of our own will can alone be the object of this inner sense; for the process of representation itself cannot over again be perceived, but, at the very utmost, only be once more brought to consciousness in rational reflection, that second power of representing: that is, _in abstracto_. Therefore also, simple representation (intuition) is to thinking proper--that is, to knowing by means of abstract conceptions--what willing in itself is to becoming aware of that willing, _i.e._ to consciousness. For this reason, a perfectly clear and distinct consciousness, not only of our own existence but also of the existence of others, only arises with the advent of Reason (the faculty for conceptions), which raises Man as far above the brute, as the merely intuitive faculty of representation raises the brute above the plant. Now beings which, like plants, have no faculty for representation, are called unconscious, and we conceive this condition as only slightly differing from non-existence; since the only existence such beings have, is in the consciousness of others, as the representation of those others. They are nevertheless not wanting in what is primary in existence, the will, but only in what is secondary; still, what is primary--and this is after all the existence of the thing in itself--appears to us, without that secondary element, to pass over into nullity. We are unable directly and clearly to distinguish unconscious existence from non-existence, although we have our own experience of it in deep sleep.
Bearing in mind, according to the contents of the last chapter, that the faculty of knowing, like every other organ, has only arisen for the purpose of self-preservation, and that it therefore stands in a precise relation, admitting of countless gradations, to the requirements of each animal species; we shall understand that plants, having so very much fewer requirements than animals, no longer need any knowledge at all. On this account precisely, as I have often said, knowledge is the true characteristic which denotes the limits of animality, because of the movement induced by motives which it conditions. Where animal life ceases, there knowledge proper, with whose essence our own experience has made us familiar, disappears; and henceforth analogy is our only way of making that which mediates between the influence of the outer world and the movements of beings intelligible to us. The will, on the other hand, which we have recognised as being the basis and kernel of every existing thing, remains one and the same at all times and in all places.
Now, in the lower degree occupied by plant-life and by the vegetative life of animal organisms, it is the _stimulus_ which takes the place of knowledge as a means of determining the individual manifestations of this omnipresent will and as a mediator between the outer world and the changes of such a being; finally, in inorganic Nature, it is _physical agency in general_; and when, as here, observation takes place from a higher to a lower degree, both stimulus and physical agency present themselves as substitutes for knowledge, therefore as mere analogues to it. Plants cannot properly be said to perceive light and the sun; yet we see them sensitive in various ways to the presence or absence of both. We see them incline and turn towards the light; and though this movement no doubt generally coincides with their growth, just as the moon's rotation on its axis coincides with its movement round the earth, it nevertheless exists, as well as that of the moon, and the direction of that growth is determined and systematically modified by light, just as an action is determined by a motive, and as the direction of the growth of creeping and clinging plants is determined by the shape and position of the supports they may chance to find.
Thus because plants on the whole, still have wants, though not such wants as demand the luxury of a sensorium and an intellect, something analogous has to take the place of these, in order to enable the will to lay hold of, if not to seek out, the satisfactions which offer themselves to it. Now, this analogous substitute is susceptibility for stimuli, and I would express the difference between knowledge and this susceptibility as follows: in knowledge, the motive which presents itself as representation and the act of volition which follows from it, _remain distinctly separate one from the other_, this separation moreover being the more distinct, the greater the perfection of the intellect;--whereas, in mere susceptibility for stimuli, the feeling of the stimulus can no longer be distinguished from the volition it occasions, and they coalesce. In inorganic nature finally, even susceptibility for stimuli, the analogy of which to knowledge is unmistakable, ceases, but the diversity of reaction of each body upon divers kinds of action remains; now, when the matter is considered, as we are doing, in the descending scale, this reaction still presents itself, even here, as a substitute for knowledge.
If a body reacts differently, it must have been acted upon differently and that action must have roused a different sensation in it, which with all its dullness has nevertheless a distant analogy to knowledge. Thus when water that is shut up finds an outlet of which it eagerly avails itself, rushing vehemently in that direction, it certainly does not recognise that outlet any more than the acid perceives the alkali approaching it which will induce it to abandon its combination with a metal, or than the strip of paper perceives the amber which attracts it after being rubbed; yet we cannot help admitting that what brings about such sudden changes in all these bodies, bears a certain resemblance to that which takes place within us, when an unexpected motive presents itself.
Ideas discussed in this chapter
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