sherlock logic

  • Someone: *doesn't like something I like*
  • Me: How DARE they!
  • My brain: they are a different person with different opinions and views
  • Me: But why wouldn't they like it??
  • My brain: because they're a different person with different opinions and views
  • Me: but-
  • My brain: different opinions and views you dumb bitch
I'm Sorry to Be the Voice of Reason

I’m seeing a lot of rumours floating around about a fourth episode.

Has this entire experience taught you nothing? There is no fourth episode. It would be a stupid marketing ploy to embed a whole Episode in subtext for us to find. The writers would not be so eager to shut us down if there were a fourth episode. There would be explicit evidence from the BBC if there were a fourth episode, not random clues and messages that mean nothing. The 404 error is a common web browser error for a broken page. We caused that with our complaints. Apple Tree Yard is just another show, and I don’t know how it got dragged into this mess. We thought there was a deeper meaning to it all, but there isn’t. There never was.

I understand everyone is grasping at any straw of hope right now, but listening to our hearts is what got them broken.

They betrayed us. They hurt the entire community.

I appreciate your efforts. You all are fantastic people who work so hard. We’ve always had to hope for queer representation in any way we can. We’ve already been feeding off crumbs. We’re accustomed to reading between the lines.

But the dog bowl is empty, my friends, and these efforts are licking dust off the floor.

And even if they were to come out with another episode or with season five, what are you expecting–a sudden one-eighty that confirms Johnlock and makes everything okay? No. They’ve shown their true colors. They don’t give a damn about us. They will continue to queerbait us for ratings. We’ll continue to make our theories about BBC Johnlock being endgame, when clearly, it never will be.

We’re an optimistic community, I know. We have every right to hope, but we no longer have reason to expect better from BBC Sherlock. The least we can do is learn from our mistake.

Moftiss doesn’t care about us. They never did.

the fact that Edward used Oswald’s father and not his mother for his little scheme has really stuck out to me and I’m taking it as proove for Edward not really wanting to “destroy” Oswald. Edward knew how important Gertrude was to Oswald and that using her would have affected Oswald even more. Edward clearly wants his  slightly petty revenge but by choosing Elijah over Gertrude he shows a flicker of something that implies that there is a line he won’t cross

The Laws of Deduction

In deduction, we use logic and generalisations to come to conclusions, or deductions about a thing or person. Many people do this subconsciously, little things like what hand someone writes with or if someone gets engaged, but never takes it to its full extent.

Of course, we all know Sherlock doesn’t use deduction. He uses a mixture of all three types, Deduction, Induction and Abduction, things we are writing posts on right now.

Deduction, however, is a science, and as with many others, has laws, things that cannot be broken and still have your conclusion come out as true. These laws are easy to learn and can help stamp out any incorrect deductions you may make, just by running them through the three of these:


From Modus ponens, the Law of Detachment basically means if a conditional statement and a hypothesis are made, a conclusion must fit both to be true.

The Latin, Modus ponens, means “the way that affirms by affirming” which basically explains the entire concept. Put simply, “if X implies Y, and X is true, so must Y”

  • X=Y is the conditional statement;
  • X as the hypothesis;
  • Y as the conclusion.

An example of this is:

  • If someone is right-handed, they will write with their right hand
  • Someone is writing with their right hand
  • The person is right-handed.

Pretty simple concept, and very useful.


Syllogism comes from Greek, and it means conclusion or inference. You have probably seen an example of it before, in the form of:

All men are mortal
Socrates is a man
Therefore Socrates is mortal

So what does it mean? Well, simply, a hypothesis of a statement combined with the conclusion of another. In the example, hypothesis 1 (H1) is “all men are mortal”  hypothesis 2 (H2) is “Socrates is a man” and if you combine H1 with the conclusion of H2 then we reach the conclusion of “Socrates is mortal” which is correct, in this case. Simply:

  • X = Y
  • Z = X
  • Z = Y

However, this law isn’t always true. There can be times when your conclusion isn’t valid, for example:

Some televisions are black and white
All penguins are black and white
Therefore, some televisions are penguins

Clearly, this is wrong. A way around this is to not form hypotheses that have no conclusive proof, only use ones that have been accepted by the majority of people, and don’t try to combine incompatible hypotheses, and also, the law itself does not have flaws, the logic is there, and it’s your responsibility to make sure YOUR logic is sound when you use this law.


This has the longest title, but is the easiest concept to understand. Contrapositive also comes from Latin, this time Modus tollens, meaning “the way that denies by denying”  the concept basically states that if a conclusion is false, so must the hypothesis.

Again, an example:

If I am lonely, there is nobody around
x, y

There are people around;
I am not lonely.

x = y
Opposite of x = Opposite of y

Another pretty simply rule, but you can see that it’s true.

And that’s it, the three laws of deduction: detachment, syllogism and contrapositive. You do not need to learn them all, but if you are planning on making deductions that heavily involve hypothesises, then I suggest asking an effort.

Technically, these are laws of logic, but many places I researched them put them down as laws of deduction, so whilst the name of them is to be debated, I’m confident that they work and are sound.

Any questions or corrections feel free to send an ask.


  • Molly: Oh come on! I just want to be ready for next week!
  • Sherlock: *unmoved* It's becoming obsessive, and you know it.
  • Molly: B-but there's so many little details to pick up on...even in those short clips! Don't you have any theories about-
  • Sherlock: Nope.
  • Molly: *excitedly* But, I mean, just based on the trailers alone, if you HAD to say who would end up-
  • Sherlock: *exasperated* We have essentially no solid evidence, which makes any theories meaningless. And besides, I am a professional detective, therefore I refuse to use my brain power to engage in pointless guessing about the fictional plot line and characters of your favorite television show which has no real bearing on our lives!
  • Molly: ... *narrows eyes*
  • Sherlock: ...
  • Molly: ...
Unreliable Narrator in The Six Thatchers is NOT Go

I’m with @sussexbound on how to interpret The Six Thatchers. I don’t think it’s a retelling for an alibi or an imagined sequence or mind palace. I could be wrong, and will be happy to accept any and all told-you-so’s in that case, but coming from a story telling perspective, odds are good that the story is meant to be accepted as is.

For me, it comes down to how stories build trust with the audience. 

Once you establish the rules of a story world, you can’t break them without also breaking the trust of the reader. It’s a contract. The reader agrees to suspend their disbelief and buy into your story world. You, in turn, promise to give them a story world that is consistent and has some kind of internal logic–even if it’s the most fantastical story world imaginable.

Sure, there’s experimental storytelling in which there truly are no rules or internal logic but Sherlock is definitely not that kind of story.

I’m going to go into more detail and analysis of this, and it got long so I’m putting it under a cut. Basically, tl;dr: Revealing that entire episodes that appear to follow the established story-world rules are either complete fabrications or mind-palace fantasies utterly destroys the viewer-storyteller contract and break trust with the audience because it’s not part of the deal the story creators set up at the beginning.

Keep reading

Logical fallacies

I was going to post the second “Thinkbox” today but I noticed that this might be more important. So I will list logical fallacies that most people fall into all the time. It is really important that these fallacies don’t cloud your mind when you try to make accurate deductions. If you, the reader notice that you may be a victim of any of these fallacies try to change your way of thinking.

Formal logical fallacies

- Anecdotal fallacy - To use personal experience as proof instead of statistics.
Example: “All women have long hair” because I’ve only met women with long hair.
A way to avoid: Realize that personal experience isn’t as accurate as statistics that have been done on many more people than you can meet.

- Appeal to probability - To think that because something is probable it’s also always the case.
Example: “You must be right handed” because most people are.
A way to avoid: The probability of something does never grantee you that it is correct.

- Conjunction fallacy - Assumption that an outcome simultaneously satisfying multiple conditions is more probable than an outcome satisfying a single one of them.
Example: “Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-nuclear demonstrations.
Which is more probable?
1. Linda is a bank teller.
2. Linda is a bank teller and is active in the feminist movement.”
Most people chose 2. But the probability of the two occurring together is less or equal to the probability of them occurring alone.
Pr(Linda is a bank teller) = 0.05
Pr(Linda is a feminist) = 0.95
Pr(Linda is a bank teller and a feminist) = 0.05 x 0.95 = 0.0475.
So the probability of her being both are lower than the lowest.
A way to avoid: Just because something seems to fit well together doesn’t mean it does. Try to think critically.

Informal logical fallacies

- Argumentum ad lapidem - Dismissing a claim as false without proof of its absurdity.
Example: “A: Atoms does not exist.
B: Why do you say that?
A: It’s ridiculous.”
A way to avoid: Don’t dismiss anything at first until you have researched the subject you think may be false.

- Argumentum ad ignorantiam - Assuming that a claim is true because it hasn’t been disproven.
Example: “A: Spirits exist.
B: No.
A: Prove that they aren’t real.”
A way to avoid: Don’t think that a hypothesis you have come up it true just because someone else can’t prove it wrong. Extraordinary claims require exceptional proof.

- Divine fallacy - You can’t imagine it to be true so it must be false.
Example: “A: Murder only happen in films
B: Why do you think that?
A: I can’t imagine anyone doing something so wrong.”
A way to avoid: Stop thinking that improbable is the same as false. Like the great Sherlock Holmes once said “When you have eliminated the impossible, whatever remains, however improbable, must be the truth”.

- Argumentum ad nauseam, argumentum ad infinitum - A topic has been discussed so much that is is seen as true or people don’t care anymore.
Example: “You have the left thumb over your right when your fingers are intervened. That means that you are right handed.”
A way to avoid: Stop accepting statements as true, conduct som research. Even if it’s on a small scale it might give you som pointers.

- Argumentum ex silentio - Conclusion is based on the absence of evidence instead of proper evidence.
Example: “A: Ah you are quiet so you did kill him.
B: But I didn’t say anything?
A: That’s why I know!”
A way to avoid: Try not to assume anything without evidence.

- Argumentum ad hominem - To attack a person instead of their argument.
Example: “A: I like ice cream.
B: Well you’re stupid.”
A way to avoid: You likely know that you’re doing this to some extent, so try to be a good debater and come up with a good counter argument. Or maybe just try to understand the other persons point of view.

- Onus probandi - To make a claim and think that other people must accept it or disprove it themselves.
Example: “A: Dogs always lick their owner when greeting them.
B: Not always.
A: Prove that they don’t.”
A way to avoid: Always try to prove your claims, it is your responsibility.

- Circulus in demonstrando - When you begin with the conclusion you’ll end up with.
Example: “A: I think he is right handed.
B: Why?
A: Emm.. Maybe because he has his watch on the left arm?
B: That doesn’t necessarily mean that.
A: It must mean that!”
A way to avoid: Try to observe first and make a conclusion based on the facts. Like Sherlock said “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts”.

- Post hoc ergo propter hoc - Assumption that correlation is the same as causation.
Example: “He had an heart attack when riding a roller coaster, so that means I will have one on the roller coaster too.”
A way to avoid: Think about the problem you have, does the correlation really equals causation?

- Fallacy of composition - To assume that the whole is true because a part of it is true.
Example: “All cells are aquatic. Therefore all organisms (which are composed of cells) are aquatic.”
A way to avoid: Like earlier, try to be critical and don’t accept something as true without research.

- Black or white fallacy - Two statements are held to be the only possible option, when in reality there is more.
Example: “The coin can only land heads up or tails up”.
A way to avoid: If you are used to problem solving this shouldn’t be to much of a problem. Try to keep an open mind when solving a problem.

- Fallacy of the single cause - Assumption that there is one simple cause of an outcome when in reality it may have been caused by multiple events.
Example: “She has a fear of spiders because she had one in her hair when she was young” When it may have been more that contributed to the phobia.
A way to avoid: Don’t assume that everything is caused by one event, try seeing the whole picture.

- Psychologist’s fallacy - Presumes you can be objective in your judgement.
Example: “A: Something will happen to you if you go out this late.
B: You only say that because I’m your daughter.”
A way to avoid: This is something that is hard to avoid, we as humans will always be biased when it comes to things we care about, so try breathing and think calmly about the problem you wish to solve if you can’t ignore it.

Even though you know these fallacies they will still affect you. No human can get rid of them all, “errare humanum est” (to err is human). But being aware of them hopefully helps you think about the problem you face a bit more.
The ones you should be most aware of is:

Anecdotal fallacy.
This I see all the time. People think that their own experiences must be what everybody else is experiencing too. This is a problem when reading studies and the results of the studies doesn’t correlate with your own experience, so you don’t believe it as much.

Appeal to probability.
Something that people new to deduction often seem to think is that it’s always foolproof. That even though most things in deduction is statistically based it must come true all the time. This isn’t the case, and new people discard deduction as something they cannot learn or something that is false and that’s tragic.

Argumentum ad lapidem.
If you as a deductionist disregard a fact as false without proper evidence you may have trouble learning the art of deduction. Being critical is good but to disregard it entirely isn’t.

Argumentum ad ignorantiam.
Likewise assuming that a fact is true because it can’t be disproven seems to be a trend in the world of deduction. I am still baffled by how many people think that long fingers is connected to piano playing (it’s the fingers flexibility that is connected to it.)

Divine fallacy.
This falls into the same category as the two above.

Onus probandi.
If you have come up with something then it’s also your responsibility to prove it to be right, if you care about it being proven to be correct.

Circulus in demonstrando.
My students in deduction have all done this mistake at least one time each. Try to observe then make deductions.

Post hoc ergo propter hoc.
Correlation does not equal causation.

Fallacy of composition.
If a deductionist have some parts of deduction figured out, well that doesn’t mean they know everything.

Black or white fallacy.
Most of the time it exists more than two options, your job as a deductionist is to figure out which of the options is more likely.

Psychologist’s fallacy.
Don’t ever believe yourself to be completely objective.

And with that, I’ll see you my irregulars.

  • Logic: even if they release The Lost Special it wouldn't get much viewers, they should've said something by now.
  • Also Logic: that's absurd if people knew about the secret episode what's there to be secret than? what is a conspiracy?
  • Also Logic: holy shit we are advertising the show ourselves how genius.
  • *5 minutes later*
  • Doubt: would I remain cool If there was no Lost Special?
  • Logic: shut up DOUBT your IQ is so low it makes me pity you stop poisoning me I'm sure there will be.
Future plans

My parents: So what is your plan for the future?

Me: Watch tv series, and fangirl.

My parents: No, what do you wanna do with your life?

Me: Watch tv series, and fangirl.

My parents: What do you wanna do for a living?

Me: I want to get paid to watch tv series and fangirl over them.

So, there are a lot of people out there bashing The Final Problem, which was a fantastic episode btw, and treating it like was the worst thing on the face of the planet.

But, you can bet your ass they would be parading about how it would be the best episode if Johnlock were to become canon.

The skull and Hamlet in Season 4

Billy the skull. The skull on the mantelpiece that Sherlock named after himself and speaks to it and thinks of it as a “friend” (“Well… I say friend”). This skull is also on the wall. It’s a staple of 221B, just as the skull on the mantlepiece is. The skull on the mantle is a substitute for John, although a poor one, being more-so a reflection of Sherlock without John, just a brain, while the skull on the wall is a constant. A reminder, of the analytical mind Sherlock possesses- a brain. Logic is commonly personified as a brain. This is what the skulls mean in seasons 1-3.

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