June 2, 192 1] 



NATURE 



425 



Biological Terminology. 



I THINK Dr. Bather (Nature, May 5, p. 3pO 

 and I may be using our words with unlike 

 meanings, but he raises an important point. To 

 use my own meanings : we describe when we 

 say what a thing is hke ; we interpret when we 

 account for it. Both these processes imply classifica- 

 tion (i.e. identification); both are necessary in 

 science; one is not superior or inferior to the other; 

 but they are different. In description we classify facts 

 and objects according to co-existences and resem- 

 blances. Thus, when we term a man a mammalian 

 vertebrate we say, in effect, that in him mammae and 

 vertebrae co-exist, and that therein he resembles 

 other animals. Is not all systematic zoology and 

 botany founded on this kind of classification, a beauti- 

 ful example of which may be found in the address 

 of any letter sent by post — addressed to a man with 

 a certain name, in a certain house, in a certain 

 street, and so on ? On the other hand, when we inter- 

 pret we explain, we link cause with effect, we formu- 

 late suppositions, hypotheses, theories, we trace the 

 connection between antecedents and consequents, 

 we try to understand. Thus we class together such 

 unlike things as the fall of apples, the rise of tides, 

 the swing of the pendulum, and the motions of the 

 planets by saying that they furnish instances of 

 gravitation ; we account for teeth and mental facul- 

 ties by attributing their evolution to natural selec- 

 tion ; we identify the blacksmith's muscles, mathe- 

 matical and golfing skill, and acquired immunity 

 against disease as results of functional activity. From 

 the nature of the case there is little or nothing of 

 this sort of thing in systematic zoology and botany. 



Description and interpretation are the warp and 

 the woof of science. The former must always pre- 

 cede the latter, for we cannot account for things until 

 we know what they are like. Some sciences {e.g. 

 mathematics and physics) are based on few facts. 

 Thus all the facts on which geometry is founded con- 

 sist of its axioms and some of its definitions. Neces- 

 sarily, therefore, this science quickly passed in its 

 evolution from description to Interpretation, and its 

 students in their mental development quickly tread 

 the same path. Their main training is in interpreta- 

 tion. They have little knowledge of facts, but great 

 skill in a particular department of thought. ^ Other 

 sciences {e.g. zoology and botany) deal with an 

 enormous number of facts; ages must pass before 

 they are at all adequately described, and every student 

 must spend years in acquiring them. His main train- 

 ing, therefore, must necessarily be In description. 

 He acquires a vast knowledge of facts, and, therefore, 

 since he knows what to look for, becomes a trained 

 observer. A mathematician may be an excellent ob- 

 server, but this skill does not necessarily flow from 

 his specific training. Indeed, it is remarkable within 

 what narrow limits his skill may avail him — Just as 

 training in a game {e.g. golf) may develop the 

 student's skill only in that particular game. Simi- 

 larly, though any zoologist or botanist may be a skil- 

 ful Interpreter, skill of this kind does not necessarily 

 flow from his specific studies. This is all that I 

 meant by the statement to which Dr. Bather takes 

 exception. 



Man Is the educable animal, but he is also the for- 

 getting animal. The things he particularly tends to 

 forget are facts. The things he tends to retain are 

 mental habits, among which are dexterities in think- 

 ing and doing. These dexterities, learned slowly and 

 with toil, are even more slowly lost — as in the case 

 of the mathematician and the cricketer. As a school- 

 boy I received some training in mathematics ; to-day 

 ■ the mathematical books in mv library are nearly use- 

 NO. 2692, VOL. 107] 



less to me. Some part of them is at my fingers' ends ; 

 the rest I cannot understand. As a medical student 

 I had to cram for examinations what seemed an 

 enormous number of facts about botany and zoology. 

 Almost all that is lost, but I can recapture any of 

 them by reference to my books. Evidently it is some- 

 times better to teach good mental habits than to 

 impart mere knowledge. No attempt was made to 

 account for the facts or natural history to me (to train 

 me in interpretation), but, fortunately for my future 

 pleasure and interest in life, I had antecedently read 

 Darwin. I doubt whether any of my contemporaries 

 were as lucky. I do not know whether teaching has 

 improved since my day ; but this I do know, that 

 while the facts of interpretative biology are abundant, 

 its hypotheses innumerable (more than two hundred 

 explanations of sex alone have been formulated), and 

 its controversies unending, it has, unlike physics, for 

 instance, next to no established truth. I know also 

 that its terminology is so loose that it Is often used 

 with no meanings or with contradictory meanings, 

 that its hostile sects ignore one another's evidence, 

 and that all sects unite in ignoring evidence derived 

 from other sciences. There is, in fact, no general use 

 of crucial testing, which is the only means by which 

 people of divided opinions can reach a common plat- 

 form and hypotheses be examined in the light of all 

 the evidence. I know besides that it is harder to 

 interest biologists in the big question of biology, or 

 in any questions not purely sectarian, than it is to 

 interest anyone else. 



This question of crucial testing is important. 

 Probably it lies at the root of most of the troubles 

 of interpretative biology. Given crucial testing, not 

 only would all the relevant facts be brought into 

 court and hypotheses be proved and, if correct, estab- 

 lished, but also the necessity for a correct terminology 

 would become clear. Dr. Bather will perhaps forgive 

 me if I become tedious in stating elementary, but 

 neglected, truth. 



Proof of a descriptive statement is furnished by 

 the facts on which that statement is founded. Thus, 

 to establish the truth that man is a mammalian verte- 

 brate it is only necessary to indicate the breasts and 

 the backbone. On the other hand, an hypothesis can 

 be proved only by fresh-, unlike, crucial facts — facts 

 of such a nature that every alternative supposition is 

 shown to be inconceivable as true. "When the hypo- 

 thesis of itself, and without adjustment for the pur- 

 pose, gives us the rule and reason of a class of facts 

 not contemplated in its construction, we have a 

 criterion of its reality which has never yet been pro- 

 duced in favour of falsehood." For example, if I lost 

 coins and supposed that Mary the servant had stolen 

 them, I should be only guessing. But if, in addition, 

 I planted marked coins and found them in her pos- 

 session, I should have proved my case with a high 

 degree of probability. Outside biology all interpreta- 

 tive science is founded on adequate crucial testing — 

 which implies an acceptance of the maxim that all 

 relevant and verifiable facts, no matter how collected 

 (by direct observation, experimentally, statistically, 

 and so on), are equal before science. Thus, in effect, 

 Newton and his successors said to themselves : " If 

 the theory of gravitation is true, stones must fall at 

 certain rates of acceleration, tides must follow the 

 moon, pendulums must swing In certain times, planets 

 must trace certain orbits, worlds must assume certain 

 shapes," and so on, until not only was the supposi- 

 tion established (by disproving alternatives), but also 

 a universe of diversified facts has been brought within 

 its range. Hence its importance. If to-day I said 

 to physicists, "Your terminology is loose and your 

 scientific methods four hundred years behind the 

 times," what would happen? I think they would 



