The science of deduction for dummies

First time seeing someone. Quick glance with a brief handshake. I know exactly who you are.

Science of deduction is such a fascinating and impressive art, but it’s rarely touched on. Compared to its counterpart: Geoguessr, the recognition for the art of deduction is unimpressive.

I’m proudly the first one to introduce you to the depth of this lost art, and this is your science of deduction 101.

Deduction vs. Induction

Deduction

Deduction is the first thing you think of when talking about Sherlock Holmes for the obvious reason.

To perform deduction, you need to have various knowledge about a subject, know what combination of factors would lead to what result, then from the given information, you can “deduce” how to get to the desired outcome.

ELI5: You know yellow mix with blue gives green. Now you have yellow and blue paint, but you want to paint a picture of grass, what do you do? Deductive reasoning: Grass is green, yellow + blue = green. You need to mix yellow and blue to paint grass!

Check out my deduction guide.

Induction

A common misconception about Sherlock Holmes, he mostly uses inductive reasoning instead of deductive reasoning.

To perform induction, you first observe the object, in details, its mechanics, how does it interact with surrounding objects, etc. From there, you make educated guesses, come up with possibilities and look for more evidence to eliminate until the last possible outcome.

ELI5: You see a picture of green grass and a bucket of yellow paint on the side. You think either there is a bucket of green paint or a bucket of blue paint somewhere, or even both. As you take a closer look, there’s a hint of unmixed blue paint on the painting. Conclusion, there was definitely blue paint involved.

Do take notice, there was no evidence suggesting there was no green paint used here. But with good confidence, you can say that the green was mixed between yellow and blue because it’s not likely that this person mixed green and then use green paint, it would make the coloring inconsistent. Although it could !

Check out my induction guide.

Does Sherlock Holmes use deduction or induction?

Although Sherlock Holmes is famous for deduction, he uses both and even more dominantly induction.

Example of Sherlock Holmes with induction

Look no further than the famous scence, either in the book or on TV show, the first meet with Dr.Watson. To make this post brief, I’ll just leave you with the link here.

Example of Sherlock Holmes with deduction

Too much writing already so I’ll give you the chasing scene in the show Sherlock BBC

Examples in real life

Deduction in real life

Deduction is more common in real life than you think. We see it in math, we see it in people making theories about how their favorite show is going to be next season, we see it when we heard our phone ring and try to guess who’s calling without seeing the screen.

I’ll also give you an example of how a deduction looks like through example of my riddle: Who broke the stand?

Induction in real life

Induction, compared to deduction, is rare. People’s attention nowadays is everywhere but their surroundings. Which makes learning to induce in real time more impressive than ever.

This is not the best example for deduction, but we can often see induction in gossiping. People take a look at something and judge on it without investigating further information to confirm their theories.

A content that I was developing on reddit in r/deduction, which everyone enjoyed and learned from it a lot, can show you a pretty good example of induction in real life. From analyzing how the receipt was folded, you can guess if it was in a bag or in a wallet. Seemingly unrelated, but it is related.

How to deduce people like Sherlock?

Imagine if you can measure your deduction skills with rating, it would be like elo rating scale in chess.

Sherlock Holmes being a grandmaster at 2800 elo, dedicated deduction and induction practitioner being international master at 2100 elo, casual deduction enjoyer at 1400 elo and people have no awareness of the subject at 600 elo.

In short, I don’t think we can ever reach the point of being Sherlock Holmes until this art is more developed and there is a prodigy born with all the information.

But, with the same comparison, just by watching deduction content, you’re twice as good as normal people already, and with some practice, you can be 3 times better than 90% of people around you.

Even though you might not be able to tell the whole story of what someone did before meeting you like Sherlock did, you might be able to pick out 1 or 2 facts that will really impress them.