Inductions?!

It has been brought to my attention, by a deeply mortified Watson, that many of his fans believe my reasoning to be not of the deductive, but of the inductive kind. The evidence they bring is my having cleared my brain attic from any philosophy which was drilled into me at school and my use of facts to draw conclusions. As I said to my Boswell, it's not all the fault of his romantic writing style: I suspect these philosopher-wannabes would not understand it anyway. That I would not know what goes through my own brain is, however, a most insulting claim and I find myself forced to disprove it.

I indulge in induction: any scientific work is such an endeavour, therefore my experiments all fall into that category. My investigations, though, allow me to stretch my deductive powers. For anyone who may still be confused about the difference, induction means discovering a general rule by way of seeing it confirmed in as many actual instances as one can gather. It is always at risk of being disproved by an evidence to the contrary.

I said, a long time ago, that my self-developed chemical test will pinpoint blood only, and indeed my experiments proved it is not subject to the shortcomings other widely used similar tests suffer. My statement was, however, much too bold – because of my enthusiasm at the time. I have not tried it on many things, after all (from gold to numerous exotic plants) and I suppose some of them could give a positive result. However no man, even in all his lifetime, would have the chance (and single-mindedness) to develop a test examining every substance in the world. And the chance of a sample's behaviour being abnormal for some reason can never be completely overruled. The best a scientist can say, with the result of his experiments and those of his colleagues, is that the probability of a reaction offering a particular result is, indeed, very high. And sometimes, being proved wrong damages more than just one's pride...but that's not the point.

Deduction, instead, starts from general truths and offers details about one specific instance, and can't be wrong, unless one's premises are erroneous themselves or one treats them illicitly.

The classic example for deductive thinking is the following syllogism:

Major premise – All men are mortals

Minor premise – Socrates is a man

Conclusion – Socrates is mortal.

If any of you are wondering why I even remember this, I may have erased the Greeks' ethics or metaphysics (they're outdated anyway), but thought-process models simply stuck (and at least when I pine for a case I know what I'm yearning for).

I'd like to draw your attention to the minor premise which is, in theabove example, hard fact.

When I offer my explanations to Watson, I leave the general rules implicit: they are obvious, after all, and I'm not prone to stating blatant things. He understands, of course, and does not need it in the open. For the dimwits who can't see it, though, I'll offer you an example:

Major premise: There is a mathematical ratio between the length of one's legs and one's height, as well as between one's footprints' distance and their legs' length (general truth).

Minor premise: The man I'm looking for left footprints whose distance I can measure (data).

Conclusion: My quarry's height is so-and-so (particular instance).

I've done it a million times. Moriarty did (no wonder, since mathematics make ample use of deductive reasoning). Frankly, I doubt the people who thought they could correct me have ever had one deduction flit through their head, no matter how long they studied the philosophers of old.

P.S. Stay tuned for the shocking revelation next chapter...