Om såkaldte deduktioner

Akronymerne er de almindeligt anvendte forkortelser for fortællingerne i Conanen.

"I see it, I deduce it.", siger Holmes i SCAN. Og det er ikke eneste gang, han benytter dette udtryk. Faktisk forekommer det utallige gange i Conanen. Nåh ja, i vores elektroniske tidsalder er utallige måske ikke ganske i overemsstemmelse med sandheden, men en computer fortæller os, at ordene "deduction", "deduce" og "deductive" forekommer tilsammen ikke mindre end 91 gange, så her er ikke tale om en tilfældighed. Og hvad er det så, Holmes deducerer. Lad os se på nogle eksempler.

Første gang vi støder på udtrykket er i STUD, nemlig i forbindelse med "The Book of Life", en artikel skrevet af Holmes:

"From a drop of water, a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other. So all life is a great chain, the nature of which is known whenever we are shown a single link of it. Like all other arts, the Science of Deduction and Analysis is one which can only be acquired by long and patient study."

Altså noget i retning af, at hvis man kender enkeltheder, in casu en vanddråbe, kan man slutte sig til en helhed, Atlanterhavet, Niagara Falls eller for den sags skyld regnvejr, et glas vand eller, hvad der i øvrigt har med vand at gøre. Et andet eksempel finder vi i SIGN, hvor det drejer sig om Watsons nyligt erhvervede ur:

"Now, I have here a watch which has recently come into my possession. Would you have the kindness to let me have an opinion upon the character or habits of the late owner?".
"Subject to your correction, I should judge that the watch belonged to your elder brother, who inherited it from your father."
"That you gather, no doubt, from the H. W. upon the back?"
"Quite so. The W. suggests your own name. The date of the watch is nearly fifty years back and the initials are as old as the watch: so it was made for the last generation. Jewellery usually descends to the eldest son, and he is most likely to have the same name as the father. Your father has, if I remember right, been dead many years. It has, therefore, been in the hands of your eldest brother."
"Right, so far," said I. "Anything else?"
"He was a man of untidy habits - very untidy and careless. He was left with good prospects, but he threw away his chances, lived for some time in poverty with occasional short intervals of prosperity, and finally, taking to drink, he died. That is all I can gather."

Samme metode som før. Ud fra en række iagttagelser slutter Holmes sig til et helhedsbillede af urets tidligere ejer, efter Watsons reaktion at dømme, åbenbart en særdeles nøjagtig karakteristik. Med andre ord går Holmes fra enkeltheden, nemlig uret, til helheden, nemlig personen. Et tredie eksempel finder vi i BLUE:

He picked up (the hat) and gazed at it in the peculiar introspective fashion which was characteristic of him.
"It is perhaps less suggestive than it might have been," he remarked, "and yet there are a few inferences which are very distinct, and a few others which represent at least a strong balance of probability. That the man was highly intellatual is of course obvious upon the face of it, and also that he was fairly well?to?do within the last three years, although he has now fallen upon evil days. He had foresight, but has less now than formerly, pointing to a moral retrogression, which, when taken with the decline of his fortunes, seems to indicate some evil influence, probably drink, at work upon him. This may account also for the obvious fact that his wife has ceased to love him."
"My dear Holmes!"
"He has, however, retained some degree of self?respect," (he continued) disregarding my remonstrance. "He is a man who leads a sedentary life, goes out little, is out of training entirely, is middle?aged, has grizzled hair which he has had cut within the last few days, and which he anoints with lime? cream. These are the more patent facts which are to be deduced from his hat. Also, by the way, that it is extremely improbable that he has gas laid on in his house."

Igen ser vi Holmes, ud fra en række iagttagelser af enkeltheden, nå til et helhedsindtryk, denne gang af Mr. Henry Baker.

Nu er det imidlertid sådan, at man i filosofi anvender to modsat rettede begreber, deduktion og induktion. Ved deduktion forstås, at man udfra et helhedsindtryk kan slutte sig til de enkeltheder, der har forårsaget helheden, medens induktion er udfra iagttagne enkeltheder at kunne slutte sig til helheden. De anførte eksempler er tydeligvis alle induktioner, og det gælder også alle andre i Conanen indeholdte 'deductions'.

Ganske interessant i denne forbindelse er det, at Holmes i SIXN anvender ordet "inductive":

"Yes, gentlemen," said he, "it is the most famous pearl now existing in the world, and it has been my good fortune, by a connected chain of inductive reasoning, to trace it from the Prince of Colonna's bedroom at the Dacre Hotel, where it was lost, to the interior of this, the last of the six busts of Napoleon which were manufactured by Gelder & Co., of Stepney."

Det turde være tydeligt, at Holmes her netop arbejder mere deduktivt end i samtlige. andre sager, idet han netop når frem til en enkelthed, nemlig den sorte perle. Og derfor overskriften: "Såkaldte deduktioner".