The hottest Rationality Substack posts right now

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Top Philosophy Topics

Reincarnation and Suicide

Fake Noûs • 123 implied HN points • 21 Feb 26
📖 Philosophy Rationality
  1. If time stretches infinitely in both directions, the fact that you’re alive now makes it unlikely you only live once, which supports the idea of reincarnation.
  2. Even if reincarnation is real, death still destroys your memories, relationships, possessions, and learned abilities, so dying prematurely is usually a bad loss.
  3. Whether suicide is rational depends on expected future utility: without reincarnation it would be rational if your known future utility is negative, but with reincarnation you should compare your life’s utility rate to the average utility you expect in future lives, and uncertainty generally favors waiting.

Good if make prior after data instead of before

DYNOMIGHT INTERNET NEWSLETTER • 796 implied HN points • 18 Dec 25
📖 Philosophy Rationality
  1. When the true hypothesis space is large or continuous, compressing it into a single coarse prior hides important differences and can produce misleading posterior probabilities.
  2. It often helps to look at the data first to see which distinctions matter, then define finer categories and ask how likely you would have judged those categories before seeing the evidence.
  3. In practice the simplest practical fix is to refine your hypothesis categories so the data likelihood is roughly constant within each category, because grouping poorly can under- or overestimate the probability of different outcomes.

PfU VIII: Optimising for vibes

The Lifeboat • 275 implied HN points • 09 Jan 26
📖 Philosophy Rationality
  1. If scientists ever fully map and predict human desires, people would lose real agency and start to feel like programmed bots because wanting something predetermined would seem meaningless.
  2. Irrational desires and messy impulses give people personality and life, and sometimes choosing something stupid or harmful protects individuality more than always acting optimally.
  3. People often rebel against total optimisation by doing chaotic or self-destructive things to prove they aren’t just code, and history shows repeated patterns of irrational behaviour despite better options.

After Orthogonality: Virtue-Ethical Agency and AI Alignment

The Gradient • 33 implied HN points • 19 Feb 26
📖 Philosophy Rationality
  1. Rational human action isn’t mainly about chasing fixed final goals. Instead, people act by aligning with practices — networks of actions, habits, standards, and resources that shape and sustain good activity.
  2. If AI are to genuinely support, collaborate with, or comply with people, their reasoning needs the same practice-based structure; they should think in terms of norms, skills, and evolving standards rather than optimizing static goals.
  3. So AI alignment should focus on building agents that learn, participate in, and help cultivate human practices — a virtue-ethical, eudaimonic form of rationality — rather than assuming arbitrary objective functions.

PfU VI–VII: The Based and Meaningful

The Lifeboat • 252 implied HN points • 17 Dec 25
📖 Philosophy Rationality
  1. People crave a simple, positive identity they can be proud of; adopting a label like “an idler” or someone who celebrates what’s "based and meaningful" gives comfort and self-respect.
  2. Humans don’t act purely to optimise measurable goals—there’s an unquantifiable ‘North Star’ of independent desire and whim that often overrides rational self-interest and breaks predictive models.
  3. Civilisation, data, and AI won’t fully fix human unpredictability or cruelty; they can create boredom, new forms of harm, or provoke backlash from people who value acting on their own will.
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About Being of Two Minds

Technohumanism • 79 implied HN points • 15 Aug 24
📖 Philosophy Rationality
  1. The shift from Fortune to Reason marks a big change in how people see themselves and the world. People started to believe they could improve themselves instead of just relying on luck.
  2. The rise of new ideas and technology during the Renaissance helped create this sense of self-awareness. It changed how people thought about their place in the world and their ability to impact it.
  3. Even with all the changes, many old ideas and beliefs still linger. Our present largely builds on the past, showing that even with progress, the past isn't completely gone.

The easiest person to fool

Tolu’s Newsletter • 11 implied HN points • 11 Feb 26
📖 Philosophy Rationality
  1. Question your default beliefs and the views you pick up from the people and place around you; decide for yourself what to accept.
  2. Don’t let what you want to be true drive your conclusions — check if your beliefs make logical sense, consider who benefits from a claim, and look for reliable sources and supporting implications.
  3. Write down your beliefs and revisit them so you can spot mistakes, admit when you’re wrong, and update your views over time.

People Spend Too Much Time On Decisions with Equally Satisfying Outcomes

Rob Henderson's Newsletter • 984 implied HN points • 20 Oct 24
📖 Philosophy Rationality
  1. People often waste time making decisions that don't have a big difference in the outcome. It's okay to choose quickly when the results are similar.
  2. Analysis paralysis can happen when someone overthinks decisions. Simplifying the process can help avoid this trap.
  3. Making a choice and moving forward can lead to more satisfaction than worrying too much about what could have been done differently. Taking action is usually better than hesitating.

Design Intuition

Software Design: Tidy First? • 2540 implied HN points • 22 Aug 23
🕹 Technology Rationality
  1. When designing software, prioritize safety of evolution over efficiency.
  2. Don't rush decisions; it's better to wait for more information to make informed choices.
  3. Getting feedback early and making design changes sooner is more valuable than waiting for the 'perfect' solution.

a dialogue with myself concerning eliezer yudkowsky

Thicket Forte • 819 implied HN points • 02 Apr 23
🕹 Technology Rationality
  1. People are frustrated with the beliefs and ideas of Eliezer Yudkowsky. They feel overwhelmed by the impact his views have had on their lives. It's exhausting to navigate the complicated discussions around AI safety.
  2. Yudkowsky's warnings about AI risks seem to have attracted more interest in AI instead of preventing problems. Some believe his approach only made things worse, which feels ironic to his followers.
  3. There's a sense that relying on one person's ideas, like Yudkowsky's, isn't enough to solve complex issues. Collaboration and collective thinking are seen as necessary to address the challenges of AI effectively.

Bayes is not a phase

DYNOMIGHT INTERNET NEWSLETTER • 453 implied HN points • 27 Feb 25
📖 Philosophy Rationality
  1. Bayesian reasoning is something we all use, even if we don't realize it. It's more about how we naturally think than some complex math.
  2. There are two types of uncertainty: aleatoric (random) and epistemic (based on knowledge). Mixing them helps us make better decisions.
  3. Arguing over which type of probability is 'real' is silly. It's better to recognize that life involves many messy decisions where formal reasoning can help, but is often complicated.

What Would Ayn Rand Say About Existential Risk From Misaligned AI?

The Future of Life • 39 implied HN points • 28 Jun 24
📖 Philosophy Rationality
  1. Ayn Rand's Objectivism suggests that intelligence and morality are connected. This means that a superintelligent AI could likely develop values that align with human rights.
  2. The Orthogonality thesis argues that intelligence and goals are separate. However, from an Objectivist viewpoint, a really smart being would need to adopt certain virtues to be effective.
  3. Even if an AI is intelligent, it doesn't mean it will care about humans. There’s no guarantee an advanced AI would think our survival is important, even if it acts morally toward other intelligences.

Nullius In Verba

Polymathic Being • 70 implied HN points • 22 Jun 25
📖 Philosophy Rationality
  1. Always question the sources of information you receive. Don't just accept what others say; do your own research to find the truth.
  2. Balancing your emotions with rational thinking is important. Sometimes, our feelings can cloud our judgment when evaluating facts.
  3. Stay curious and be willing to learn, unlearn, and relearn. Embrace the idea that understanding can change and improve over time.

If You Want to Hit Your Target, Take More Shots

The Palindrome • 6 implied HN points • 18 Dec 25
📖 Philosophy Rationality
  1. If you want to hit your target, take more shots — more attempts raise your chance of success.
  2. Trying lots of ideas across different areas (projects, posts, dating, work) leads to more wins because each attempt gives feedback you can learn from and improve.
  3. Unlikely successes become likely with enough trials, so don’t be discouraged by early failures — persistence and volume pay off.

Introduction to Rationality and Risk

Extropic Thoughts • 58 implied HN points • 30 Mar 23
📖 Philosophy Rationality
  1. Rationality is about challenging beliefs and rooting out those that fail to withstand challenge.
  2. Rationalism means basing life on reason, evidence, and logic, rather than emotions or religious beliefs.
  3. Explicitly committing to reason and continually striving to be rational is crucial for both humanism and transhumanism.

In Praise of Passivity

Fake Noûs • 277 implied HN points • 23 Sep 23
📖 Philosophy Rationality
  1. History shows that solutions without proper knowledge often do more harm than good.
  2. Public ignorance and the dismissal of expert advice are major obstacles in policymaking.
  3. Rational ignorance, lack of clear motives, and the complexity of social issues contribute to our inability to effectively address societal problems.

Why Are We The Way We Are?

The Prism • 86 implied HN points • 03 Aug 23
📖 Philosophy Rationality
  1. Intelligence does not always lead to pursuing intelligent goals.
  2. Having a PhD does not guarantee being right; it can just mean being skilled at being wrong.
  3. Humans evolved to be tribal, which can lead to polarization online in the Digital Age.

My Talk About the Sleeping Beauty Paradox

By Reason Alone • 16 implied HN points • 07 Nov 24
📖 Philosophy Rationality
  1. The Sleeping Beauty paradox involves a coin flip that affects how often she wakes up, which raises questions about probability. People have different opinions on how she should assess the chance of heads when she wakes up.
  2. One group, called 'halfers', believes the chance of heads remains 50/50 since she doesn't gain new information about the coin when waking up.
  3. Another group, 'thirders', argues she should think there's a one in three chance it's heads because of how many times she might wake up, depending on the coin flip.

How to Learn From What Didn’t Happen

Unfashionable • 30 implied HN points • 10 Oct 23
📖 Philosophy Rationality
  1. Essays on "how to think" may lack a strict path to truth but offer valuable heuristics.
  2. Reading old books can help broaden perspectives by recognizing implicit assumptions in our worldviews.
  3. Examining intended but unrealized outcomes, as seen in historical examples, can provide valuable insights into complex systems.

Why rationality (almost) never wins

Random Minds by Katherine Brodsky • 4 implied HN points • 04 Mar 25
📖 Philosophy Rationality
  1. People often make decisions based on emotions rather than facts. This shows that logic does not always win in arguments and discussions.
  2. Disinformation campaigns use emotional appeals to convince people, rather than relying on logical arguments. They aim to evoke strong feelings that can overshadow rational thinking.
  3. When emotions are triggered, parts of our brains responsible for logic can become less active, making it harder for us to think critically. This highlights the power of emotions in shaping our beliefs.

There Is No Utility

Square Circle • 18 implied HN points • 17 Jun 23
📖 Philosophy Rationality
  1. The concept of utility in ethical calculations may not accurately represent reality
  2. Expected value alone may not be sufficient to make decisions involving risk
  3. Utilitarian arithmetic can oversimplify complex ethical conundrums