Dec. 1st, 1887.] 



SCIENTIFIC NEWS. 



Facts, when not quite overlooked, are too often seen and 

 recorded erroneously. I would not speak of such errors 

 without a confession of having contributed to them, or with- 

 out the fair motive of wishing to urge the best means for 

 avoiding the like of them. For remember that many of 

 them were made, or are being made, by men as honest as 

 we are or ought to be, and as fairly in the pursuit of know- 

 ledge. 



It would need some volumes to relate all the sources of 

 error in scientific observation. I will mention only one, 

 for I think it is the most frequent, and I should like you to 

 be always watching against it. It is the habit that we have 

 of inserting something of our own, something of our 

 beliefs, of our expectations, nay, even of our wishes, into 

 that which we think or say that we observe. We expect 

 facts or events to agree with what we believe that we 

 know, and we make light of the differences and exaggerate 

 the likenesses ; we take no thought of what we call acci- 

 dental exceptions ; we think them unmeaning — as if any- 

 thing in nature could be without meaning — and we do not 

 half observe them. In philosophy we can separate things 

 from thoughts — the object from the subject ; but in ourselves 

 and in ordinary life they are mingled in every act of con- 

 sciousness and reflection ; and sometimes it is only by care- 

 ful self analysis and by habit studiously gained that we can 

 separate them and observe simply and accurately. 



There is a very common proverb that "seeing is believ- 

 ing," and many, as if trusting it, say, " I must believe what 

 I see." It is often unwise to do so ; for the sight, without 

 the aid or control of other senses, is often fallacious. But 

 there are many in every walk of life who, when they say 

 " [ believe what I see," might just as fairly say, " I see 

 what I believe " ; and these, though they are usually in the 

 wrong, are usually the most positive in their assertions. 

 They believe what they wish, and tlien they see what they 

 believe ; and then they become unable either to see or to be- 

 lieve anything contrary to their wishes — anything contrary 

 to what they call their clear convictions. Well, as a man may 

 see an unexpected likeness of himself in a caricature, so may 

 we all see a defect of our own exaggerated in people such as 

 these. We are all apt to see what we expect to see — to 

 think that the knowledge already gained is so sure that that 

 which is next to come must exactly agree with it. Our 

 safeguard must be in careful scientific study — in the habit 

 of observing without prejudice and with self-distrust, 

 always remembering that everything brought within the 

 range of human knowledge is brought within the much 

 wider range of human error. 



And here let me add that, however much the mechanism 

 and other external helps for observation have of late been 

 improved, our mental powers have not increased in the 

 same degree ; we are in ourselves as likely to observe erro- 

 neously as were our predecessors ; in this sense we are not 

 wiser than our fathers. It may even be doubted whether 

 the improvements in the means of observing be more than 

 in proportion to the much larger field and the more minute 

 facts within reach of which we have been brought. It is 

 comparatively easy now to see and do many things which 

 used to be difficult or impossible ; but it is not, therefore, 

 easier to see and do new things. The higher we rise on the 

 hill of knowledge the steeper and the more difficult does the 

 ascent become. And we are not yet near the summit ; it 

 reaches up to heaven. 



I might speak of many means of helping ourselves in the 

 cultivation of the power of accurately observing, such as 

 reading — which is, perhaps, of all the most important — and 

 of drawing, collecting specimens, and many more ; but I 

 will speak of only one, which is far too often neglected. 

 You will find it, I think, essential to scientific accuracy that 



you should have the habit of recording very carefully your 

 observations and all the chief facts connected with them. 

 No one should wholly trust his memory in such things ; it 

 may lose the facts, or, worse still, may gradually alter them ; 

 for, as belief and expectation and other mental s'ates can 

 affect the impressions which we derive from things even 

 when they are present before us, so and much more can they 

 affect those which we try to reproduce in memory. The 

 self is here alone in all its fallibility. 



I have heard a very truth-loving person say that if he had 

 ever told the same story ten times he always became doubt- 

 ful whether he was telling it rightly. You may do well to 

 remember this when you are telling cases. You know the 

 game in which a story is handed on through ten or more 

 persons, and then there appears very little likeness between 

 that told by the first and that told by the tenth. None of 

 them have wilfully changed the facts, but every one has been 

 a little inaccurate, and the inaccuracies have accumulated. 

 There is some measure of the same difficulty of exact re- 

 presentation of facts by each person's own memory, and we 

 cannot too carefully guard against it. Inaccuracy, it has 

 often been said, has done more harm than falsehood has ; 

 and this is certainly true in our own sciences. 



Now there can be no better safeguard against these mis- 

 chiefs than the habit of making studious and careful records 

 of the things that you observe. It should be a constant 

 habit of student life; and, let me earnestly add, these 

 records should be made whenever and as completely as they 

 can be while you have before you that which you are to 

 describe, so that you may write down the very few facts that 

 you are observing, and may revise them whenever you have 

 a chance in the presence of the same or similar facts. 



I hope I shall not make your future studies seem utterly 

 hateful to you by thus speaking of them as if they were 

 only full of pitfalls and occasions of mischievous error. 

 Really there are none that you may not avoid ; but you 

 cannot be too cautious ; so I shall continue my advice, for 

 most of us need to be still more careful when in our studies 

 we pass, as we always do, from observing to thinking, and 

 to what we believe to be reasoning. John Hunter, it is re- 

 ported, used to say to those who would draw conclusions 

 rather than search for facts, " Don't think ; try." Happily 

 for science, he often did not observe the rule ; he was one 

 of the very few who could really sometimes think a truth 

 far beyond that which could be observed ; but we are not 

 all like him, and for all of us the saying is an excellent one, 

 " Don't think ; try." Do not suppose that j'ou can safely 

 think what must follow from what you know ; try whether 

 it is so. Do not think that you can safely explain what you 

 observe by any hypothesis or theory; and that having thus 

 explained it, there is no need of studying it further. Collect 

 new facts and "try" your theory by them, and if the 

 theory and the facts do not agree, stick to the facts ; thej' 

 will accumulate into larger truths. We must have theories, 

 or explanations as they are called, of many of the facts 

 which we observe. We need them to help us to the best 

 ways available for arranging the facts, as we need book- 

 shelves for books; and they are useful for suggestions as to 

 what, and where, and how to search for new facts. But 

 here, or hereabout, should be the limits of their use ; and 

 the using of theories for purposes beyond these is full ot 

 danger, and often a great hindrance to progress. 



As one looks back on the relations between the collection 

 of facts in practice and the explaining of them in accordance 

 with the theories which were in successive times accepted, 

 and which were commonly called " general principles," and 

 regarded as safe guides in the treatment of disease, we may 

 fairly doubt whether the gain or the loss were the greater 

 You will see that in each successive generation every fact 



