# Derrick Farnell > Independent researcher and a writer, mainly interested in how the mind works. Public Ghost content for AI and LLM tooling. This file includes a bounded export of public pages first, then recent public posts. Append `.md` to any post or page URL to get the content in Markdown (for example, `/example-post.md`). ## Pages ### About URL: https://www.derrickfarnell.site/about/ Last updated: 2026-08-04T17:41:31.000Z ![Selfie of Derrick Farnell on a hike.](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/size/w1600/2026/05/IMG_20190619_122911--2-.jpg) ## Hello, I'm Derrick Farnell. I'm an independent researcher and a writer, mainly interested in how the mind works. I live in Edinburgh, Scotland. ### [ Read my articles ](https://www.derrickfarnell.site/articles/) → ### Articles URL: https://www.derrickfarnell.site/articles/ Last updated: 2026-08-26T16:16:01.000Z - [ ![](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/size/w1600/2026/08/Gemini_Generated_Image_uwgo4vuwgo4vuwgo.jpeg) How Belief Works An ongoing series on the psychology of belief ](https://www.derrickfarnell.site/how-belief-works/) - [ ![](https://images.unsplash.com/photo-1580207837202-7a1ff3cb12f7?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wxMTc3M3wwfDF8c2VhcmNofDMwfHxhbyUyMG5hbmd8ZW58MHx8fHwxNzgzNzYwNzM4fDA&ixlib=rb-4.1.0&q=80&w=1600) The Theory of Evolution by Natural Selection in One Sentence Darwin's beautifully simple idea ](https://www.derrickfarnell.site/the-theory-of-evolution-by-natural-selection-in-one-sentence/) ## Subscribe Submit Email sent! Check your inbox to complete your signup. ### Contact me URL: https://www.derrickfarnell.site/contact-me/ Last updated: 2026-06-10T08:24:06.000Z You can email me at [derrick.farnell@gmail.com](mailto:derrick.farnell@gmail.com). ## Subscribe Submit Email sent! Check your inbox to complete your signup. ### Support my work URL: https://www.derrickfarnell.site/support-my-work/ Last updated: 2026-08-26T08:06:08.000Z ![Photo of a home desk with a laptop connected to a monitor.](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/2026/08/PXL_20260804_115522839-EDIT2-3.jpg) My workspace My dream is to work full time as an independent researcher and a writer – I currently rely on two part-time jobs. However, I also want my writings to remain free and ad-free. So please consider helping fund my work – including helping me pay for books and online resources – by making a one-time or monthly donation of your choice. If you have any questions or problems, [email me](https://www.derrickfarnell.site/contact-me/). ### How Belief Works URL: https://www.derrickfarnell.site/how-belief-works/ Last updated: 2026-08-26T16:13:22.000Z ![A photorealistic extreme close-up of a young man's eye and brow. His head is turned to the viewer's right, with his gaze fixed straight ahead.](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/2026/08/Gemini_Generated_Image_uwgo4vuwgo4vuwgo.jpeg) Image generated by Google Gemini 'Belief … is the central problem in the analysis of mind.' – philosopher Bertrand Russell ([source](https://www.gutenberg.org/files/2529/2529-h/2529-h.htm#link2H%5F4%5F0015)) The prevailing understanding of how belief works is wrong – and not just a bit wrong, but the-Sun-goes-around-the-Earth wrong. And just as the reality of the relationship between the Sun and the Earth had profound implications for our understanding of the cosmos, the reality of how belief works has profound implications for our understanding of the human mind. But this reality is so counterintuitive that it can, ironically, seem unbelievable – as did the idea that the Earth isn’t the stationary centre of the universe but sweeps around the Sun while spinning about an axis. This ongoing series reveals the truth about how belief works and explores its implications. [Share](#) - [What Is Belief?](https://www.derrickfarnell.site/what-is-belief) - Next three articles: - How Beliefs Form – Part 1 - How Beliefs Form – Part 2 - The Impossibility of Degrees of Belief *Previously published versions of these three articles are available on* [*a live archive copy of this site*](https://sites.google.com/view/derrickfarnell/articles/how-belief-works)*. Although I think the core logic in these versions is sound, I decided that the form of the arguments presenting that logic needs improvement, along with the writing.* *The standalone article \[Article X\] will eventually be incorporated into this series.* ## Subscribe Submit Email sent! Check your inbox to complete your signup. ### Donation form URL: https://www.derrickfarnell.site/donation-form/ Last updated: 2026-07-28T16:11:03.000Z ← [Back to article](javascript:history.back%28%29) If you have any questions or problems, [email me](https://www.derrickfarnell.site/contact-me/). ## Posts ### The Theory of Evolution by Natural Selection in One Sentence URL: https://www.derrickfarnell.site/the-theory-of-evolution-by-natural-selection-in-one-sentence/ Last updated: 2026-08-26T08:09:13.000Z ![Photo of scene inside a tropical forest.](https://images.unsplash.com/photo-1580207837202-7a1ff3cb12f7?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wxMTc3M3wwfDF8c2VhcmNofDMwfHxhbyUyMG5hbmd8ZW58MHx8fHwxNzgzNzYwNzM4fDA&ixlib=rb-4.1.0&q=80&w=2000) Photo by [Nick van den Berg](https://unsplash.com/@nngvandenberg) Charles Darwin's theory of evolution by natural selection, published in 1859, explains that all of life on Earth today evolved over the eons from common ancestors. And the essence of this grand theory can be captured in a single sentence: *Within a species there's always slight random variation in the hereditary traits of its members, and given the competition to survive and reproduce, those variations that happen to be most conducive to doing so will naturally tend to become widespread in the species.* So the process of evolution by natural selection involves the *non*\-random 'selection' by nature of particular random variations. And the continuous occurrence of random gene mutations means that random variation – the fuel of this process – is ever-present. These mutations have several causes, including gene copying errors. How conducive a variation is to survival and reproduction depends on the environment in which the members of the species are living. So when the members become separated into two populations – perhaps by a mountain range or an ocean, or simply distance – and face different environments, natural selection leads the populations to evolve in different directions. And they may eventually diverge so much that they can no longer interbreed, thereby becoming separate species. Thus, the steady accumulation of innumerable small changes over billions of years has led to the extraordinary complexity and diversity of today's plants and animals. This beautifully simple but powerful theory, so often misunderstood and misrepresented, explains how the appearance of design in living things arose from a mindless process that's as natural as water flowing downhill. ![Sepia portrait of an old man with a large white beard.](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/2026/08/1_GzO33cwrGNl59BiQNmj5OQ-1.jpeg) Charles Darwin (1809–1882) [Share](#) ### Support my work ![Photo of a home desk with a laptop connected to a monitor.](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/2026/08/PXL_20260804_115522839-EDIT2-3.jpg) My workspace My dream is to work full time as an independent researcher and a writer – I currently rely on two part-time jobs. However, I also want my writings to remain free and ad-free. So please consider helping fund my work – including helping me pay for books and online resources – by making a [one-time or monthly donation](https://www.derrickfarnell.site/donation-form) of your choice. You can also support my work just by [sharing this article](#). ### Feedback I view my published writings as still works in progress, and welcome feedback about both the writing and its content, *however minor*. I also welcome feedback about the website. You can comment below or [email me](https://www.derrickfarnell.site/contact-me/). ### Referencing this article If referencing this article, you should include the date of reading, as the content can change. Also, you can [save the current version in the Internet Archive](https://web.archive.org/save) and then link to the archived copy. ### Article history Past versions of this article are available in the Internet Archive [here](https://web.archive.org/web/20260000000000%2A/https://www.derrickfarnell.site/the-theory-of-evolution-by-natural-selection-in-one-sentence/) – and, for previous locations, [here](https://web.archive.org/web/20250000000000%2A/https://www.derrickfarnell.site/articles/the-theory-of-evolution-by-natural-selection-in-one-sentence) and [here](https://web.archive.org/web/20240000000000%2A/https://www.derrickfarnell.site/miscellaneous-articles/the-theory-of-evolution-by-natural-selection-in-one-sentence). There's also [an archive of this article on GitHub](https://github.com/derrickfarnell/derrickfarnell.site-archive/commits/main/posts/the-theory-of-evolution-by-natural-selection-in-one-sentence.md). ### Acknowledgments This article was inspired by the book [*The Moral Animal*](https://www.google.co.uk/books/edition/The%5FMoral%5FAnimal/MuI%5FDVZ1Xo8C?hl=en&gbpv=0&kptab=overview) by Robert Wright, which presents the theory of evolution by natural selection in one sentence in the first chapter. My presentation of the theory in one sentence was based on Wright’s. My understanding of the theory of evolution by natural selection comes mainly from the books [*The Selfish Gene*](https://www.google.co.uk/books/edition/The%5FSelfish%5FGene/WkHO9HI7koEC?hl=en&gbpv=0) and [*The Blind Watchmaker*](https://www.google.co.uk/books/edition/The%5FBlind%5FWatchmaker/zHc9PgAACAAJ?hl=en), both by Richard Dawkins. The point that evolution by natural selection is as natural as water flowing downhill comes from the book [*The Adapted Mind*](https://www.google.co.uk/books/edition/The%5FAdapted%5FMind/SxX4gRzOS6oC?hl=en&gbpv=0), by Leda Cosmides and John Tooby. ## Subscribe Submit Email sent! Check your inbox to complete your signup. ### What Is Belief? URL: https://www.derrickfarnell.site/what-is-belief/ Last updated: 2026-08-26T08:08:37.000Z ![Photorealistic close-up of a hand-written note stuck to a fridge door with a magnet, reading 'buy milk'.](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/2026/08/Gemini_Generated_Image_ka6z7cka6z7cka6z-1-1-1-1.png) Image generated by Google Gemini *This article is part of the ongoing series* [*How Belief Works*](https://www.derrickfarnell.site/how-belief-works/)*, which is best read in order.* We all know what it means to believe something, from the significant, such as the belief that humans are apes, to the mundane, such as the belief that there's no milk in the fridge. Indeed, belief is one of the most basic concepts of human psychology. Yet it's also one of those everyday concepts that can be surprisingly difficult to define, like art or happiness. Any attempt must include that it's a psychological state involving a claim. In the above examples it's believed that *humans are apes* and that *there's no milk in the fridge*. Although claims are often asserted by someone, whether verbally or in writing, a believed claim hasn't necessarily been asserted by anyone, even the believer. Upon looking inside our fridge, we can form the belief *There's no milk in the fridge* without anyone, including ourselves, *asserting* on this occasion that there's no milk in our fridge. Also note that the term *belief* can refer to either the psychological state or the believed claim. That is, it can refer to either believing something or something believed. In the first sense, my belief *There's no milk in the fridge* is a different thing from someone else's belief *There's no milk in the fridge*, regarding the same fridge, because they're separate psychological states existing in different heads. But in the second sense, they're the same thing. So the term *mundane belief* can refer to either believing a mundane claim or a mundane claim that's believed – and likewise for the term *significant belief*. However, we often use the term *belief* by itself to mean a significant claim that's believed, whether moral, political, religious, historical, philosophical or scientific. For example, when we refer to defending our beliefs, we're referring to defending particular significant claims we believe. This series concerns our belief of any kind of claim, however significant or mundane. Other examples of mundane beliefs are my current beliefs *I’m in my flat*, *I'm sitting on a chair at my desk*, *I'm typing these words*, *It's Tuesday morning*, *It’s sunny outside*, and *I went for a hike along a river yesterday*. Given that the psychological state of belief involves a claim, the following definition can seem as obvious as it is simple: considering a claim to be true. But although this definition can seem irrefutable, it's fatally flawed – as I’ll explain in the next article, on how beliefs form. [Share](#) Next article: How Beliefs Form – Part 1 (forthcoming) [How Belief Works](https://www.derrickfarnell.site/how-belief-works/) ### Support my work ![Photo of a home desk with a laptop connected to a monitor.](https://storage.ghost.io/c/86/cd/86cd0066-a957-488f-b0e4-a5bc82f2723d/content/images/2026/08/PXL_20260804_115522839-EDIT2-3.jpg) My workspace My dream is to work full time as an independent researcher and a writer – I currently rely on two part-time jobs. However, I also want my writings to remain free and ad-free. So please consider helping fund my work – including helping me pay for books and online resources – by making a [one-time or monthly donation](https://www.derrickfarnell.site/donation-form) of your choice. You can also support my work just by [sharing this article](#). ### Feedback I view my published writings as still works in progress, and welcome feedback about both the writing and its content, *however minor*. I also welcome feedback about the website. You can comment below or [email me](https://www.derrickfarnell.site/contact-me/). ### Referencing this article If referencing this article, you should include the date of reading, as the content can change. Also, you can [save the current version in the Internet Archive](https://web.archive.org/save) and then link to the archived copy. ### Article history Past versions of this article are available in the Internet Archive [here](https://web.archive.org/web/20260000000000%2A/https://www.derrickfarnell.site/what-is-belief) – and, for previous locations, [here](https://web.archive.org/web/20250000000000%2A/https://www.derrickfarnell.site/articles/how-belief-works/what-is-belief), [here](https://web.archive.org/web/20250000000000%2A/https://www.derrickfarnell.site/how-belief-works/what-is-belief) and [here](https://web.archive.org/web/20251001000000%2A/https://www.derrickfarnell.site/how-belief-works/a-note-on-the-term-belief). There's also [an archive of this article on GitHub](https://github.com/derrickfarnell/derrickfarnell.site-archive/commits/main/posts/what-is-belief.md). ## Subscribe Submit Email sent! Check your inbox to complete your signup.