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Our Systems of Belief

Neil deGrasse Tyson

Lesson time 13:37 min

Every personal system of belief contains identifiable biases that impact the ability to think scientifically. Neil talks about two of these biases and how inner beliefs can have a significant societal and scientific impact.

Neil deGrasse Tyson
Teaches Scientific Thinking and Communication
Renowned astrophysicist Neil deGrasse Tyson teaches you how to find objective truths and shares his tools for communicating what you discover.


- So we talked about cognitive bias. There are other biases you can have, but we wouldn't necessarily call them cognitive bias, because they're not a product of some weakness in the wiring of the human brain. They come about from some other influence that takes place-- cultural, political, religious influence. Everybody has bias. Some people have more bias than others. But if, after all these experiments have been conducted, there's convergence in a result, then you have successfully winnowed out the influence of bias on that scientific research. No one was without bias. Just be ready to get your stuff checked, and be ready to just abandon your cherished thoughts and ideas in the face of conflicting evidence. [MUSIC PLAYING] So let me start out with something I'm just calling a personal truth. So a personal truth is something that you hold to be true no matter what anyone else thinks of it. And almost all religious tenets would come under that category. Is Jesus your savior? Is Muhammad the last prophet on earth, and you are certain of that? Do your ancestors keep watch on you and look after you? These are tenets that exist in different religions that are deeply and strongly held by the faithful among those religions. Personal truths. In a free country, especially one where religious freedoms are protected, go right ahead. Have whatever personal truth you want. Of course, providing it doesn't constrain or remove the freedoms of others. That's why we're calling it a personal truth. OK, if you have a strong personal truth, and that personal truth overlaps something that can be tested scientifically, then you have to just be aware that you can end up confronting information that is objectively true-- that is, true regardless of who looks at it-- and it could conflict with your personal truth. And it can manifest, once again, by thinking you're special, but not from a, I'm a special human, but, I'm part of a group that is special. My religion is more special than your religion. My country is more special than your country. My way of thinking is more special than your way of thinking. It actually distorts your ability to interpret reality because you have an unjustified level of confidence in a particular world view you have adopted. What I mean by unjustified is you participate in this mindset because it makes you feel good about yourself and this group that you're a part of. And in order to feel good, in almost all cases, it involves denigrating other groups. Nazi Germany-- that was a personal truth. Personal truth is Nazi Germans are superior in every way to everyone else in the world. This is a personal truth that they-- and they believed it down to their bones and acted on the world based on that belief system. So what they all have in common is that they derive from belief systems, whether or not their belief system has a religious foundation or otherwise. The good thing about science is that it's true whether...

About the Instructor

With a hit talk show and bestselling books, Neil deGrasse Tyson is one of the most popular figures in modern science. Now the influential astrophysicist teaches you how his mind works and how he connects with audiences. Learn to think like a skeptic, open your own mind through scientific literacy, distill data, and navigate bias to discover objective truths—and deliver your ideas in ways that engage, excite, and inspire.


Students give MasterClass an average rating of 4.7 out of 5 stars.

More than learning something 100% new it has confirmed some things I already believed to be true. Also, it rekindled my interest in science and the scientific method. Excellent course, congratulations to NDT and hopefully we´ll see much more of him in the future.

Whether or not I agree with all of Mr. Tyson's conclusions, I enjoy hearing his thought processes. He is entertaining and thoughtful. He reinforces the need to deliberately listen to and consider thoughts and beliefs that oppose our own. Not necessarily for the sake of argument but more to understand where we are deficient.

Super enjoyed this talk, I believe the workbook will give me more info about the details. thanks

I learned how to better my communication skills. I learned a different way of looking at the world and people.


Rui V.

Great video, even though Mr. Tyson's attachment to the scientific belief system is evident. It seems that even mankind's greatest minds cannot see that everything is the same and anything is possible. I'll just say that if you place a ball of cheese in a stable orbit around the earth, you will have a moon made out of cheese.

Here's a satirical piece, if you care to read it, that aligns with this lecture. "Measure of ‘Lowest Common Denominator‘ Among Americans Near Zero" “Any lower and we’ll be flat lining,” says Owen Richards, head of statistical analysis at More On, a California think tank. The term represents a measurement of the level of the least discriminating audience or consumer group. The study titled ‘Reasoning In the Population’ (RIP) paints a grim picture of a growing segment of Americans. “Left to their own devices and the misinformation they get from them, many adults are having difficultly coming up with even one fact based thought.” Richards said. The study of 2,700 subjects shows the correlation of the growing use of ego driven social media, a hyper political climate and the need to fill a bloated 24/7 news and entertainment cycle as some of the factors responsible for the downward spiral. “To get a base line we pored over thousands of Facebook postings and Twitter feeds as well as stories in the New York Post, interviews at public urinals and Fox News. The findings were horrific. For example, the large following of You Tube egg videos and people unwrapping a box of merchandise is not an aberration.” Richards also points to the popularity of Donald Trump as indicative of the decline in perception and reasoning. He cites the acceptance by Trump supporters of his string of near truths, contradictions and outright lies as examples of the lack of basic analytical thought among millions of Americans. “What we see happening is a worldview based on fiction posing as facts that seeps down to become core beliefs. Across all segments of society people are believing what they want to if it fits into a narrative they’re comfortable with. “Unfortunately, that can result in an inability to consider any conflicting yet pertinent data. About the only thing those in our study could agree on was the alphabet, although not necessary in letter order. “I’m afraid,” Richards added, “the days of enlightenment are long over.” Gil Prowler writes satirical and social commentary..

Jonathan G.

I know I might be in the minority here being a Christian who loved this lesson from Tyson. I thought this lesson was very good and I wish most of my friends would watch it. I personally love science and I love to find the truth in everything, even if that confronts my own personal belief. I found myself getting angry with friends who will post misleading political posts that aren't even true, but they believe it just because they saw it on a news platform that confirmed their own beliefs. I see this being true with my conservative friends that watch Fox News or my liberal friends that watch MSNBC. It's hard to find people that actually do the research and figure out what is actually going on. Objectivity is a rare skill for people to have and its even rarer for people to recognize their own bias. I recognize that there are plenty of things that I am biased on.

Bernardo F.

I think there's a really narrow space where you can have a belief but still be conscious that it is a bias. I mean, I abandoned the catholic religion many years ago, but stil sometimes I remember my ancestors, of talk to them even if I know that they don't exist anymore, they aren't in another realm (or at least that I know)... but I feel it as a habit. But even if I do that, I don't believe in paranormal phenomena. Or sometimes I may refer to "mother nature", nontheless I'm pretty sure that there's not an invisible force out there. Don't missunderstand me, I do agree with Neil, and I found why this lesson is the top-rated. It's just that if you have some habits that you know are personal beliefs and don't let them influence your critical thinking, you can believe whatever you want.

Dane A.

thank you dr Tyson for this lesson, i will remember this. anything built on what is not objective truth/ real will fall down eventually, any argument that is far away from the objective truth, you can easily deconstruct.


This lesson is so profound and I've been rewatching. Understanding and remembering that my religious or political beliefs can lead you to being controlled. Mr Tyson is truly helping me explore my mind more daily. One of my favorite lectures thus far.

M S.

Great episode, have to rewatch it, again and again, to remember about identifiable biases. A great way is to ask myself, "what don't I know?"

Kristi B.

I loved his example with Abraham Lincoln. My astronomy professor described the incident better, but NDT described it perfectly in regard to personal truth vs. objective truth and being a skeptic when someone tells you something. Lincoln was a really smart dude if he could use his knowledge and reasoning to disqualify what a preacher (who had some kind of credible reputation at the time) said.

Brian H.

9:30 “When the legend becomes fact, print the legend,” (from “The Man Who Shot Liberty Valance).

Royce D.

I love NDT! This entire course is pretty worthless. what I mean is the people who need to hear this, won't. My guess is the only people here reading this comment are already huge fans of yours like me those people likely already agree with just about everything you are saying. Sadly I don't think there are many who will truly learn from this which is a shame because what a world this would be if everyone understood the core concepts of this course. Sorry for the strange comment, thanks for making this!