A BIO-PHYSICAL PROBLEM .sx AN ancient conundrum , " Why does a chicken cross the road ?sx " had for its answer , " Because the bird wants to get to the other side , " and in ancient times the answer was no doubt considered duly satisfactory , but in these modem times , some members of one school of scientific opinion , namely the Behaviourists , roundly reject the answer .sx These Behaviourists assert that it is unscientific to talk about " wanting to get to the other side of the road " ; it is teleological , it is vitalistic , and when teleology and vitalism come in at the door , Science flies out at the window .sx They contend that the phenomenon stated in the question is merely a tropism , simply one of the innumerable cases of response to stimulus .sx Thus , green plants bend towards the light ; they respond to the stimulus of light by bending towards it ; they are positively phototropic .sx Similarly moths are positively phototropic and fly towards the candle flame .sx Certain caterpillars are positively phototropic when they are young and climb .sx upwards to the top leaves of the plant , but when they are older they become negatively phototropic and crawl down again .sx The case of the chicken is also an instance of response to stimuli .sx The complex of sights , sounds and smells coming from the other side of the road , is the stimulus to which the bird responds .sx The chicken is positively other-side-the-road-otropic , or clothing the naked Anglo-Saxon words in decent Hellenic dress , the chicken is positively tapikeinohodotropic .sx The whole phenomenon is a case of tapikeinohodotropism , a simple case of response to a tapikeinohodotropic stimulus .sx And that is why the chicken crosses the road .sx The Behaviourist's answer is very impressive , especially to those who cannot read Plato in the original , but closer examination shows that it is not an answer at all but only a reply .sx The term " phototropism , " when translated into the crude and frank terms of our mother-tongue , becomes " turning with reference to light .sx " When the Behaviourist sees that moths turn towards the light and not away from it , he names the behaviour " positive phototropism .sx " If he says that moths fly towards the light because they are positively phototropic , he is merely saying that they fly towards the light because they fly towards the light , and his reply is a useless tautology .sx If he says that the moth's behaviour is clue to phototropism , he has personified the name of the behaviour and has credited the personified name with having brought about the behaviour .sx In Anglo-Saxon words , the moth's turning towards the light is due to turning-towards-the-light-ness , and the reply is as tautological as before .sx It is quite correct to say that the chicken crosses the road because it is positively tapikeinohodotropic and that its behaviour is due to tapikeinohodotropism , but as both forms of reply simply assert that the bird goes to the other side of the road because it goes to the other side of the road , the Behaviourist might just as well have saved his breath .sx It looks suspiciously like a case of intoxication by exuberant verbosity .sx It is of course possible that botanists and zoologists are peculiarly liable to verbal intoxication , and that chemists and physicists are free from such distressing weaknesses .sx The possibility is worth investigating , but as our ancient conundrum deals with matters much too complex and difficult for the chemist and physicist to tackle , we will descend to their level and ask some simpler questions .sx For instance , we will ask , " Why does carbon combine with oxygen ?sx " To this the chemist replies , " Because of their .sx chemical affinity " and we are shocked to find that the chemist suffers from exactly the same deplorable weakness as the biologists .sx " Chemical affinity " is the name given to the behaviour of chemical entities , and in the chemist's reply , the name of the behaviour has been personified and credited with bringing about the very behaviour of which it is merely the name .sx The reply says , when translated , that C combines with O because C combines with O , or that C combines with O because of their joining-together-ness .sx The chemist , in fact , is just as bad as the biologist with his tropisms .sx Our last hope is the stern but sometimes rather mystical physicist .sx " Why , " we ask him , " do stones fall to the ground ?sx " He replies , " Because of Gravity , or perhaps it would be more accurate to say , because of the force of Gravity " and our last hope is gone .sx The word " gravity " is only the name of the behaviour which in familiar language we call " falling together .sx " Gravity is the falling-together-ness of things , and to say that stones and earth fall together because of the falling-together-ness of things is a pure tautology .sx To say that the fall is due to Gravity is to personify the name Gravity and ascribe to the name the power of an agent who brings about the action .sx The physicist is right when he says that he raises his hat from his head by the force of Physicist , but when he says that his hat falls back on his head by the force of Gravity he is committing the error of personification .sx Our conundrum therefore still remains unanswered in spite of the replies which have been offered .sx The replies are all invalid because of errors of tautology and personification .sx Whether it be the biologist's tropism , or the chemist's affinity or the physicist's forces the same fallacies are committed and the same phenomenon of verbal intoxication is observed .sx Now , when we find that a whole company of very worthy people has become verbally intoxicated , it is both charitable and reasonable to conclude that their drink has been tampered with , and we quickly find that this is the case in these instances .sx The question , " Why does a chicken cross the road ?sx " contains an insidious and powerful word which cannot be swallowed by a scientist without very serious consequences .sx The word is " Why .sx " The moment we remove it and substitute " How , " the question entirely loses its scientific deleteriousness .sx How does the chicken cross the road ?sx and How does C combine with O ?sx and How do stones fall to the ground ?sx are all questions to which the scientist can give answers .sx How ?sx simply asks for an account of the behaviour ; .sx it asks for the sequence of material events , and the more extensive and detailed the sequence can be made the more completely is the question answered .sx On the other hand , the word Why ?sx asks for something quite different .sx It asks for the idea , the thought , the feeling or the desire which anteceded the material sequence of events , and which gives the sequence a meaning .sx The difference is rather subtly and charmingly illustrated in the case of a mother whose little boy has fallen down .sx If she wants to know the material circumstance which anteceded the tumble , she asks , How did you fall down ?sx but if she wants to know the thought , the desire , the motive which anteceded the troublesomeness of her child , she demands , Why did you fall down ?sx and not only is the question different but the tone is different too .sx If the word Why ?sx demands a non-material , a mental antecedent to the event about which the question is asked , Science cannot supply it , because a non-material entity , an entity which does not occupy space , which does not occur in clock-time , which is not capable of being conceived as made up of parts , particles or waves , is scientifically non-existent in the sense that it is incapable of being apprehended by any means at the scientist's disposal .sx Anyone who asks a Why ?sx question of a scientist either does not understand the question he is putting or else he understands it much too well .sx If the scientist does not see the catch in the question he is forced into tautology and personification , and Phototropism , Affinity and Gravity are made into living souls and duly perform their imaginary work .sx There is , however , another way in which a reply can be given to the question , " Why does a chicken cross the road ?sx " We might reply , " The chicken crosses the road because the light rays which fall on the bird's eye from the other side of the road , stimulate the optic nerve , which stimulates the brain cells , which stimulate the bird's leg-muscles , which propel the bird across the road .sx " This reply contains neither tautology nor personication and bears no trace of teleology or vitalism , so it is a strictly scientific answer .sx Nevertheless , although the answer is a real one , it is not an answer to the question asked , but an answer to another question altogether .sx The word " because " means " it is caused by , " and when we use the word we are in effect converting the question into the form , " What is the cause of the chicken crossing the road ?sx " and this gives us the opportunity of choosing one or other of the two meanings of the word " cause .sx " The " cause " of any event is the event which invariably .sx antecedes and never succeeds the event in question .sx The antecedent event may be a non-material entity , a thought , an act of will , or it may be a material entity .sx If we want to know the former , we ask , " Why did that event occur ?sx " ; if the latter , we ask , " How did that event occur ?sx " ; if we do not realize the double meaning of the word " cause " we ask , " What is the cause of the event ?sx " and in the confusion which arises either meaning can be adopted and the answer framed accordingly .sx In the cases of the chemist and physicist it does not matter much if they do indulge in tautologies and personifications .sx If the physicist likes to call the falling of bodies towards each other , Gravity , and then say that bodies fall because of Mr. Gravity , and that Mr. Gravity exerts himself to move them about , and that bodies are moved by the force of Mr. Gravity , no one is any the worse , because all experience shows that Mr. Gravity's desires are strictly proportional to the mass of the body which he moves , and Mr. Gravity has never been known to vary from this admirable consistency .sx The mental antecedent to the fall of a stone , namely Mr. Gravity's will regarding it , is a constant which can be neglected , even if it did exist .sx Similarly , it is not inexcusable to talk about individual bodies like cubic centimetres of water , " exerting a force .sx " It is never necessary to worry about whether any particular cubic centimetre of water will be a bit cantankerous to-day and refuse to depress the pan of the spring balance to the usual extent .sx It can be safely assumed that its intention is a constant , and that it will be as obliging as usual .sx When we come to the biological sciences of Botany and Zoology , however , we find that the personification of modes of behaviour is very far from being harmless .sx If moths flew into the candle-flame as invariably as stones fell down a well , it would be a relatively harmless thing to personify the name of the mode of behaviour and say that the moths flew into the flame because of Phototropism or even by the force of Phototropism .sx But moths don't ; a lighted candle will not clear a room of moths ; moth-ball manufacturers still flourish ; the frenzied cry of , " Oh !sx there's a moth .sx Kill it !sx " is still to be heard even in homes where candles are in use .sx The physicist and chemist may be allowed to answer Why ?sx questions by using tautology and personification .sx Such questions as " Why does a stone fall to the ground ?sx " are meaningless pseudo-questions to which no reply can be given except the pseudo-answer which the question deserves .sx But the question , " Why does a moth fly towards the candle-flame ?sx " and " Why does a chicken cross the road ?sx " may be real questions , even though the scientist cannot answer them , and it is not legitimate to reply to them with a pseudo-answer .sx The facts of habit and instinct , however , appear at first sight to negative the view that there is any real meaning in a Why ?sx -question. All plant behaviour is instinctive , and a vast amount of animal behaviour also , including that of man .sx