​
    There's nothing wrong with hearing an interesting Einstein quotation and putting it on your blog or T-shirt or whatever.  But don’t grab stuff from inspirational-quote websites or image searches you’ve done on the words “Einstein”, “genius” and “intelligent”.  There’s a couple of minor reasons not to do it and one really fundamental one.  Minor reasons first:

Problem 1: Original words, language and context
      Take one of the most famous Einstein quotations ever: “God does not play dice with the universe.”  Quoted alone this is a bit misleading.  Originally he wrote, in a letter to Max Born dated December 4th 1926, “I, at any rate, am convinced that he is not playing dice.” 
      Well, actually it was: “Ich jedenfallsbin überzeugt, dass er nicht spielt Würfel“ because Einstein spoke mostly German. 
      Also, to put the above quotation in context, Einstein was not religious.  He was deistic and when he talks about God he is not talking about the God worshipped in any religion.  In fact, he never really uses the word God in his writings, referring instead to “the old one“ which meant "whatever caused the laws of nature to be this way".  So the first problem with quoting Einstein is that it’s often a translation taken out of context.
 
Problem 2: Accuracy
      Check out the following Einstein quotations.  You’ve probably heard some of them:
 
1) Insanity is doing the same thing over and over and expecting different results.

2) Everyone is a genius.  If you judge a fish by its ability to climb a tree it will live it’s whole life believing it is stupid.

3) Education is what remains when you forget everything you learned in school.

4) Not everything that counts can be counted and not everything that can be counted, counts.

5) Our technology has surpassed our humanity.
 
      Einstein never said any of these things.  Or anything close.  They’re either fake quotations or quotations originally spoken by someone else.  That last one about technology comes from none other than Jeff Goldblum.  It’s something his character says in the movie Powder (1995) and while it's a thought-provoking quotation, it’s not Einstein‘s.
​

    Check out the quotation I have at the top of my blog.  I’m not quoting it because it’s Carl Sagan and I want everyone to go “oooo, Carl Sagan said it“.  I’m quoting the phrase because I think it sums up the aim of my blog in a better way than I could have come up with.
      The real problem is that Einstein’s name has become synonymous with genius, intelligence, insight and wisdom.  That’s the reason lots of people quote him. 
    Thing is, the worst way to support an argument is to say “this clever person agrees with me.“  Who cares if a clever person agrees with you???  Seriously.  You don’t make a point or conclude an argument by showing which famous and clever person is on your side.  This is what’s called the argument from authority and it’s a bad way of deciding truth.  You make your point by giving good evidence.  End of story.

Image credits
Kanye West: Amazonaws
Goldblum: Shakefire
Einstein: Sophie Delar
300: Internet video archive

Disclaimer/Disclosure
    As soon as you say the word feminism a lot of people get defensive.  I’ll bet some of you are already feeling anxious just from the title. Generally I don’t want my blogs to get political, but the way I see it, feminism isn’t always a socio-political stance, it can sometimes just be the word we use to  mean "I'm sensible". 
    If we define feminism as the belief that women should have the same rights and opportunities as men and that women's contributions to society are just as valuable...then it’s a shame we need to even have such a word – it’s like having a word for “I believe everyone should be allowed to drink water”; it’s something we should just assume everyone automatically thinks. So I guess I would call myself a feminist. If women are not treated with the same respect as men,  not given the same opportunities as men and are not celebrated the same way men are then that's an affront to 50% of the population and needs to be rectified.
    The majority of men (I’d like to believe) recognise that a society where women have equal rights and treatment is for the benefit of everyone. So why is feminism still talked about? Women are allowed to vote, get an education, get employed, testify in court, start a business etc. etc. But are there things for which they are not yet treated equally? I think unfortunately the answer is yes. The numbers vary depending on where you source them but the picture is similar in a lot of places:
 
29% of MPs in the UK are women
70% of minimum wage earners in the UK are women
4.6% of Fortune 500 CEOs are women
30% of speaking characters in the top 100 grossing films are women
29% of female actors in the top 500 grossing films wear revealing clothes (only 7% of men do)
22% of U.S. parliamentarians are women
24 states have never elected a female governor
98% of teenage girls feel under pressure to look a certain way (for boys it’s 30%)
92% of teenage girls feel they ought to lose weight.
 
    To be clear, I don’t think there are groups of men sitting in dimly lit halls cackling and deciding “how can we suppress women today?” Maybe we're just seeing those numbers because it’s a hangover from an older society which did devalue women (or rather, only valued women for their baby-making), and we just haven’t fixed it yet? I'm not sure. I'm no sociologist. What I can talk about  is the fact that you see similarly unbalanced numbers in the STEM fields.
    I should  point out that these issues are rather domesticated compared to how women are treated in other parts of the world. There are bigger injustices to tackle than the under-representation of female scientists, but I figure I might as well tackle the problems in my own back yard before I go on a crusade the fix the planet.
    I’m also conscious of the fact that I’ll probably receive a backlash for this blog post.  Some people will think I’m overreacting to the issues, some will think I’m not reacting enough.  Some people will think I’m only saying it to impress women, some will think I’m writing the whole thing sarcastically to attack women. I don't know how to help you with interpretation, I can only write honestly.

What the problem might be...
 
13% of STEM jobs in the UK are held by women.
49% of schools in the UK send no female students to study Physics at University.
39% of year 13 Maths students are female.
8.5% of year 13 Computing Science students are female.
Physics is the 19th most popular degree choice for girls (for boys it's 4th)
There are 1.8 times as many men studying Maths at university (i.e. almost twice as many)
 
Is this a problem?
    Some people might argue that by highlighting women as "missing" from STEM I am, indirectly, being anti-feminist.  After all, if men and women are equal then a workforce of men is equal to a workforce of women.  Why am I singling women out? 
    Well here’s the thing: women and men are equally valuable but they aren’t biologically identical.  Men and women are anatomically, hormonally and neurologically different so treating both sexes identically is a recipe for disaster. Giving both sexes the same opportunities however might lead to really good things.
    If you study differences between men and women’s brains you tend to get one of two approaches.  Either you hear that men are from Mars and women from Venus (i.e. utterly different) or you hear that men and women are the same in every respect and the idea of masculine and feminine thought is a social construct.  The reality is far closer to the second option; men and women’s brains are, on the whole, the same. But there are subtle differences. 
    These differences don’t affect key aspects of cognition like memory, pattern recognition, synthesis, puzzle solving etc. but they do present some minor variations in how men and women approach problems. That means the more women you have working in STEM the more variety of thought you have, which has to be a good thing.
    But are those numbers above like that because women are being discouraged from STEM or are they like that because women are naturally less likely to choose it? If it's the former then we have a problem we can fix, if it's the latter then we still have a problem but it's one that we have to just accept and move on with.
 
What if women just don’t want to study STEM?
    Perhaps the reason so few women choose STEM is simply because they aren’t interested.  If that’s genuinely the case then fine, we’ll soldier on with the gender divide. Women should have the right to choose not to go into the STEM subjects. I suppose what I’m interested in is the fact that very few women go into STEM subjects when they are allowed to! Why is that happening? I honestly don't know but I'm starting to suspect that a number of factors play into it,
    A female student of mine recently told me a story about an exchange she had with an engineer while looking at University courses.  She expressed an interest in engineering and he literally responded with “You can’t do engineering right because you’re a girl.”  

    Mainly I'm curious how this guy managed to survive the meteor impact which got rid of the other dinosaurs.  Apparently rampant sexism does still exist in the STEM community, but I’d like to think (perhaps I’m naïve) that it’s not usually as flagrant.  I would like to believe that most women aren’t told “you can’t study this subject” and that if they are told that, they don’t believe it. But I have to wonder how many women avoid STEM because they know they'd be an outsider?  
    Unfortunately this makes the problem harder to combat because it’s harder to pin it down a societal influence, but I can give some examples.  Do you remember that episode of The Simpsons where Lisa is campaigning against Malibu Stacy dolls promoting gender stereotypes?  Did you know that’s based on a true story?
    In 1992, Mattel released Teen-Talk Barbie.  Two of the messages some Teen-Talk Barbie dolls said were:  “Will we ever have enough clothes?” and “Math class is tough.”  That’s a lot of little girls whose toys – allegedly representing how teenagers talk – saying girls value clothes and find math difficult. 
    I’m sure many girls grew up to hate maths and love clothes on their own.  But how many got it in their heads “that’s what a teenage girl is supposed to say and think” and ended up conforming to a cultural role? I should point out that Mattel did recall the dolls, but it’s the fact that nobody found a problem with the messages before release which worries me. 

    The US department of education found that girls who have a strong “self concept” of themselves in Science are more likely to choose it as a career. Tell kindergarten girls they aren’t suited to STEM however and it might be harder to persuade them otherwise when they’re in high school. I'm singling Barbie out, but there might be other ways we unconsciously bias younger girls against STEM. 
    If we were to put a huge push on getting girls into STEM, we might find that most of them don’t choose it after all. If so then fine, we'd just have to accept it. But at least we'd know for sure. The key issue is that women are given the freedom to choose fairly.
    If the gender divide in STEM is a consequence of natural inclination then I guess we'll just have to swallow that pill, but if it's a cultural thing then we'd better get right on it, because STEM is suffering! So, let's say, for the sake of example, that it is about culture. If that does turn out to be the case...
 
How do we solve it?
    Complaining about things is necessary, but if you don’t suggest solutions, it’s just a whinge.  I also think it’s important to keep an optimistic outlook (when the world looks unpleasant, try to believe it can be better).  I’m not claiming I’ll fix the world with my internet blog, but I would like to suggest some practical ideas for your consideration and discussion.  These are in no particular order of importance.
 
Support Primary School Teachers with STEM training
    A 2015 report by Brunel University found that a third of Primary school teachers don’t feel confident teaching Science.  Primary school teachers are usually children’s first contact with STEM education and around 87% of them are women.  That means a significant number of children are seeing a woman who doesn’t feel confident in STEM. 
    This is not the primary school teachers' fault at all.  Primary school teachers are amazing and I couldn’t do their job.  But I know if I’m teaching a subject I’m less confident with, it comes across in the lesson, kids pick up on it and the lesson doesn’t go as well.
    So we need to start offering more training for primary school teachers who don’t feel as confident in STEM.  Give them lesson ideas, resources, send them to workshops, train them how to do interesting demos, run practical activities and extend kids’ scientific thinking.  Provide primary schools with engaging Science books and make sure girls and boys get access to them.  Send the message early on that women can be confident in STEM, the same as boys. 
 
More Programs to support women in STEM and more exposure for those that exist
    The Athena Swan Charter (as an example) is a group dedicated to championing and promoting women’s careers in STEM.  They defend women who feel they’ve been unfairly treated and reward institutions who are supportive of women’s issues.  We need more attention given to such programs.
    I’m, not necessarily saying government should fund these programs (although I think it would help) but I think public recognition and acknowledgement would go a long way.  These organisations do need more funding and they need more exposure in the media.  Give them enough funding to make television adverts maybe?  Get some celebrity endorsement to raise the profile.  The more people are aware of programs like Athena Swan, the more they are funded and the more capability they have to make changes. 
 
Representation of female Scientists in the media
    At the moment, a lot of Scientists depicted in TV and movies are men.  The Big Bang Theory has, in fairness, introduced two female characters who are scientists, but only several seasons in…and they aren’t really good depictions of Scientists (just like the guys in fact).  Generally Scientists in the media are portrayed as caricatures (boffins/nerds/lunatics) but as such they are usually male. 
    There have been some outstanding female Scientist characters in recent sci-fi movies though, Gravity, Interstellar, and Sunshine all feature well written, confident, intelligent female Scientists who aren’t there to look attractive and be romantic foils for the men.  It’s definitely a promising sign. 
    To me one of the best Scientist characters ever (one of the characters who really made me realise what it is to think like a Scientist) was Ellie Arroway from Contact.  I saw the film when I was about 13 years old and read the book many years later, both times I found her inspiring.  A woman inspiring a boy to think Science is cool?  Shock horror.
    Arroway is evidence-driven, skeptical, confident and isn’t defined as the romantic interest of a man.  She is fierce, brilliant, ingenius and stands up for facts when everyone else is looking for a political angle.    

​    Also, I’ll just say it: a female doctor in Doctor Who would be great.  The doctor is often a very Scientifically minded character.  He solves problems through thinking, analysing evidence, using prior knowledge and experimenting.  At the moment, his companions are female, so let’s try flipping it.  Let’s have a female critical-thinker solving her way through adventures.  And let’s not worry too much about whether men will find her pretty.  Let’s worry about whether men and women will find her inspiring.
 
Include current Science in our textbooks and syllabuses
    We have to teach children the basic laws of Science and they were discovered over the past few centuries – largely by men.  Girls in school hear the names of endless dudes doing great things and might get the unconscious impression that this is a subject for guys (as opposed to one which was historically only studied by guys). Usually Marie Curie and Rosalind Franklin get a cursory mention but that’s it. 
    There is a simple fix for this.  Start including up-to-date Scientific discoveries in the syllabus and textbooks.  Take astronomy for instance.  Starting with people like Annie Jump Cannon and Henrietta Leavitt, astronomy is full of pioneering female names.  Why not teach kids about Dark Matter and Vera Rubin?  Why not teach them about Carolyn Porco, one of the most widely respected and listened-to Scientists in the world today?  Or how about teaching older students about Emmy Noether (one of my all-time favourite scientists) or Chien Shiung Wu and what they did for theoretical physics?  
    Sure, we have to teach pupils about the genius of Charles Darwin, but let’s extend that to the courageous fieldwork of Jane Goodall.  Science is full of inspirational people with inspirational stories and a lot of them are currently happening with female names.  Science education does need to include the history and the basics, but there’s a lot of important Science happening right now in our lifetimes.  And guess what, a lot of it’s being done by women! 

Ultimately
    There are other things which could and should be done to solve this problem.  I’ve ignored outright sexism in the lab because that’s easier to spot and other people write about it better.  Obviously men shouldn’t make misogynistic comments, harass women sexually or only value them for their looks…duh.
    I genuinely believe the best thing for civilization is Scientific education for all. So let’s get more girls to feel they have a shot at getting into Science because it will be good for Science itself and, therefore, the human race…which contains both women and men.

Image Credits:
Solvay conference recolourised: ​Sanna Dullaway
What feminism is: Blended with Hope
Angry-looking George Carlin: ​Pop Matters
​Teen-Talk Barbie: Divine Caroline
Ellie Arroway: Reel Life Wisdom
Bernadette from ​The Big Bang Theory: Worn on TV 
Carolyn Porco: TED
Stick figures of people doing math: Randall Munroe

   
    The word ignorance is used as an insult but it shouldn’t be.  It doesn’t mean stupid or rude, it just means “lacking knowledge”.  I’m totally ignorant of the works of Skrillex for instance.  I know it's a thing but I know practically nothing about it.  Pointing out when someone is being ignorant therefore doesn’t attack them at all, it reminds them of an important fact: 
 
                          No matter how much you know, there is always more which you don’t! 
 
    A student once asked me an interesting question which turned into a thought-provoking discussion:
 
Student: Are there parallel universes?
Me: Nobody knows.  There are lots of Physicists looking for them but nobody has any idea.
Student: But what do you think?
Me: I think nobody knows.
Student: If you had to guess.
Me: I wouldn’t.
Student: But what do you believe?
Me: I believe I don’t know.
Student: What if I held a gun to your head and forced you to decide.
Me: Why are you holding a gun to my head, I thought we got on?  
Student: Just say I was and you had to pick.
Me: My guess would be completely random and I'd only be doing it to stop you pointing a gun at me.
Student: So, go with your gut feeling.
Me: My gut feeling is nobody knows.
Student: You aren’t allowed to say that, now choose.
Me: OK, fine.  Let’s say yes, there are parallel universes?
Student: Why did you pick yes?
Me: Because I like the idea of parallel universes and I think that would be cool.
Student: Thanks, also how come you’re just so awesome Mr James?
Me: Well, I’m naturally that kind of guy.
Student: And also, your blogs are really well written.
Me: I know.
 
     It’s an interesting exchange and it highlights a key point.  Giving the answer “I don’t know” to a question is never satisfying.  If the student had asked which Scientist first suggested the idea of parallel universes that would be different, I would say Isaac Newton (in his book Opticks).  But the question they asked was a speculative one: do parallel universes exist?  We have no evidence one way or the other, so nobody knows.  At all.
    Other speculative questions are things like: Do aliens exist?  How did life on Earth originate?  How long will the human species last?  The only answer anyone can give to such questions is “I don’t know”.  However, you can talk about possibilities and probabilities until your face goes purple. 
    For instance, I think it’s very probable alien life does exist.  But evidence always trumps conjecture.  If you don’t have any evidence, you don’t know the answer to the question.  And it’s ok to be like that. 
    The problem is, ignorance often looks like weakness, even though it’s actually a healthy state of mind to be in.  I was once in a cinema and a woman behind me was mouthing off about something awful and stupid and offensive, so I got involved.  She asked me a question at one point and I said “I have absolutely no idea”.  Her response was: “And you’re proud of your ignorance are you?” 
    Well, not really, but I’m not ashamed of it either.  I’m just honest with myself (or at least try to be).  Obviously I didn’t say anything that cool or collected during the argument.  I just snapped back with something caustic and cutting.  I’m a grown-up you see.

​    Ignorance is a good thing to admit, especially if you're doing Science.  There’s a wonderful scene in the Hollywood blockbuster Avatar which illustrates the point.  The main character is asking the spiritual leader of the Na’avi clan why they haven’t been able to teach humans their ways.  The response given sounds like mumbo-jumbo, but it’s actually brilliant: “It is hard to fill a cup which is already full.”  In other words: you can’t teach someone who thinks they already know the answers.
    The same is true when we’re carrying out a Scientific test.  If we go in feeling like we know what the results are going to be we’re biasing ourselves.  We should always start at zero belief (ignorance) and wait for the evidence to convince us one way or the other.  We can have our hunches but the whole point of Science is to test them. 
    Rene Descartes carried this out to the extreme in the 17th Century.  He decided to start at complete ignorance, refusing to believe anything, and see what he could convince himself of.  He came to the conclusion that he existed, God existed, and mathematics existed.  Whether we agree or disagree with Descartes’ conclusions, his intentions were noble: start with no belief and wait to be convinced.

    ​Admitting and owning up to ignorance can be really hard, particularly when you’re a teacher.  You spend a lot of time telling people what you know so it feels weird to talk about how much you don’t know.  It’s not easy to get the balance right. 
     As a teacher I usually make it clear to my classes that I know a lot about the subjects I’m teaching.  It’s not to boast mind you, it’s to help students feel at ease in my classroom.  If students have confidence in their teacher’s knowledge they’re more likely to feel they can trust what happens.  So I try to establish the fact that I know a lot about what I teach.  And I do.  I’m really proud of my subject knowledge.
     But I know less than 0.00001% of the Scientific knowledge out there!  This is one of the cool things about Science: even when you know loads about it, you’re still not even close to running out of stuff to learn. 
     Sometimes I’ll joke with my classes and say “I know everything” but it’s understood, I hope, that I really don’t know much about anything.  My knowledge is dwarfed by others and dwarfed further still by the Universe itself.  And that's OK.  Even the most knowledgeable people in the world are mostly ignorant of it.  And it’s wise to remember that, particularly when we’re engaging in debate.  

​Image credits: Angry teenager

    You know when you want to reach into a television screen or the pages of a book and slap someone in the face?  Of course you do.  You're filled with ontological rage just like everybody else.  Well, that happened to me recently when I caught a few moments of The Big Bang Theory.  In this particular episode, Sheldon visits his mother and mentions Evolution .  The following exchange takes place:
 
     Sheldon’s mother: Everyone’s entitled to their opinion.

     Sheldon: Evolution isn’t an opinion, it’s fact.

     Sheldon’s mother: And that is your opinion.​

​    The issue I have isn’t with evolution or people who deny it (well, I do take issue with that but that's a battle for another day).  It’s the fact that Sheldon’s mother thinks she is entitled to an opinion about the reality of the natural world.  The crime she’s guilty of is not understanding what opinions are for.
    We can’t really blame her for being ignorant about evolution.  Evolution is often poorly taught and many are oblivious to what it says.  What concerns me more is a fundamental confusion she is showing about when an opinion is required.  But it turns out, she's not alone.  We teach the difference between fact and opinion in schools, but rarely do we teach children when to use them.     
Out of the mouths of babes
    Recently I visited a primary school and did an experiment where we measured which chemical would fizz the most in a given reaction: A, B or C.  The pupils all took guesses and it was a three way split.  After conducting the experiment it turned out to be C.  
    Everything was going well until I asked the class: “So, are we allowed to carry on believing A or B if the evidence says it’s C?”  Rather surprisingly they all said yes.  I was puzzled so I asked them to explain why they were saying that.   The reason they gave was something they were clearly proud of: “everyone’s allowed to have an opinion and there’s no such thing as a wrong one”.   
    That's definitely true.  Opinions, by definition, are subjective and you are entitled to any.  But it would seem the mantra of valid opinions has come to mean "everybody can believe whatever they want, even in the face of contrary evidence."  
   It really got me thinking.  Is it a good idea to teach people they can believe whatever they want?  I might believe murder is justified.  Or that a certain medicine contains poison and I prevent sick people from taking it.  Or that it's OK to torture animals.  Some opinions could lead to significant harm to others (if you want depressing proof of that, check out the case of Natalie Rippberger).
    Also, if an opinion is something which can’t be right or wrong, then surely it can’t apply to a situation where there is a right and wrong answer.  The square root of 64 is always 8.  You can’t have an opinion about that and say it's 15.  I think we need to teach a more realistic message:

An opinion can’t be wrong, but you can’t have an opinion about reality.  ​
​

   
​    A few weeks ago, several news websites including the BBC,  The Independent and The Guardian ran a story on the latest Scientist to analyse Yeti samples.  Stories of the abominable snowman, a mysterious creature inhabiting the Himalayas, have been circulating for about 200 years now.  Sightings have been reported and tracks have been photographed but, at the time of writing, nobody has caught a yeti.  So the question is: do we believe in Yetis?
     Let me be clear, I would love yetis to be real.  And, just to put it in context, cryptid creatures really are discovered occasionally.  Giant squids and okapis were both mystery-creatures until fairly recently.  Could yetis be next on the list? 
    Well, maybe.  It would be foolish to say “yetis definitely don’t exist” because someone might find a yeti carcass the next day and you’d look like an idiot.  Yetis aren’t a matter of opinion either because they either do or don’t exist and, strictly speaking, it’s a testable idea; we really could carry out an enormous experiment to confirm or disconfirm their existence (observing every square foot of the Earth simultaneously would do it).
     For now though, we have to be honest and say we don’t know if yetis exist.  But if we wanted to place a likelihood on it - to say whether such a creature was probable or not - how could we do so?  At present, yeti evidence falls into three categories.
 
     1) Body samples: People have found chunks of bone, flesh and hair claimed to belong to a formerly living yeti.  The most recent investigation on such a sample was carried out by Eliecer Gutierrez and Ronald Pine, who published their results in Zookeys issue 487 (which you can find online for free).  The conclusion they came to via DNA analysis is that supposed yeti hair samples can be identified as coming from Himalayan brown bears...or, they come from yetis after all but yeti hair matches bear hair by coincidence.
 
     2) Footprints: A lot of photographs and casts have been taken of unusual tracks found in Himalayan snow.  The size of the footprints, their angle and the distance between them don’t match any known animal.  So, none other than Edmund Hilary (the first man to reach the summit of Everest with Tenzing Norgay) investigated the tracks and explained his findings in the January 13th 1961 edition of Life magazine.
     Hilary followed several apparent yeti tracks and discovered that they belonged to dogs.  As the dogs raced through the snow, the bounding of their feet meant several paws would hit the powder in the same place at the same time, creating enormous shapes at unusual distances and angles from each other.  So the footprints could be explained as belonging to dogs…or, they were made by yetis and the dogs happened to be in the area.
 
     3) Sightings: Since the early 1800s, many people have reported seeing hair-covered creatures walking in the Himalayas.  Himalayan brown bears (and a few other bear species native to the area) will sometimes walk on their hind legs.  Add to that, human sensory systems working poorly at higher altitudes where there is less oxygen, and a higher rate of hallucination.  It seems quite likely that the various sightings have been bears and blurry eyes…or, yetis.

    We have a decision to make.  We can explain all the yeti information as bears, dog-footprints and human misperception…or there really is a species of unidentified ape-creatures living in the Himalayas who have never been reported in detail prior to the 19th century, leave no identifiable remains, leave no droppings, have never been clearly photographed or filmed, and have managed to survive in a harsh environment for two hundred years while somehow keeping their population density extremely low. 
    This gives us two competing hypotheses which both explain the evidence completely.  So it’s time to use Occam’s razor, a philosophical suggestion attributed to the medieval philosopher William of Occam.  It's pretty straightforward:
 
             “The hypothesis with the fewest assumptions should be chosen until you know better”.
 
     Occam’s razor says if you have two equally plausible, equally evidenced hypotheses and no way to distinguish between them, go with the one requiring the least number of mental leaps. 
     This does NOT mean the simpler hypothesis is definitely correct.  Indeed, it might wrong.  But until evidence comes along to support one explanation over the other, Occam’s razor says you’re better off going with the simpler one.
     In the case of yetis we either accept a hypothesis in which bears exist, footprints can be misinterpreted and human eyesight can be fooled (a hypothesis with no leaps of faith) or we accept that never-before-seen animals exist and have avoided detection against all odds (quite a big leap of faith).

    The simplest explanation isn’t always the correct one, that's true, but the number of times an unusual explanation has turned out to be right is fairly small.  If we don’t use Occam’s razor (and go with the more outlandish idea) then we're introducing the notion that mental gymnastics to explain an otherwise simple finding are a good way to go.  We might suggest that Yetis can turn invisible when they hear us coming.  Or turn into trees, or even fly.  Perhaps they can teleport to the moon.  All these hypotheses are consistent with the evidence: no yetis found, but they all require us to take enormous mental leaps in order to hang onto them.  At this point it starts to sound more like desperation rather than reason.
     Occam’s razor can be misused or misrepresented sometimes.  It isn't a way of deciding if a hypothesis is true.  It’s also not an unbreakable law of Science.  But when you have two plausible explanations for something, the chances are the more straightforward one is going to be right.  While I want Yetis to be real, I have to go with Occam’s razor and not my preferences.  Are yetis real?  I don't know, but unfortunately, I doubt it.


Image sources:
Yeti by Phillippe Semeria 
Himalayan Brown Bear by Zoo Hluboka
William of Occam by Moscarlop