The Mathematics of Morality

Use maths to make the future better

5-week, donation-based (i.e. free if needed!) online program exploring how you can use mathematics to best help others and multiply your positive impact.

Dates: Next cohorts 30th June - 3rd August 2025. Apply by 1st May!
Who: Smart, curious, and ambitiously altruistic students aged 15-19 in the UK or Ireland who haven’t yet started university
Applications: Apply here and tell us a bit about yourself, your accomplishments, and your aspirations, then take a fun puzzle test
All applicants will receive access to our self-paced online courses even if you are not selected as a Finalist
NEW! Top Finalists (accepted course participants) can apply to participate in a selective August Fellowship with additional custom mentorship, funding, and support!

Apply Now

What you can expect

Facilitated discussion groups with a cohort of smart, curious students

Talks and Q&As with professionals using maths to tackle pressing problems

Mentorship and up to £1,000 in grant funding for selected Fellows to pursue follow-up projects

Support with UCAS applications and Oxbridge interviews

9/10 participants would recommend

Surveyed at the end of our first cohort, Fellows gave an average of 9.0/10 for how likely they would be to recommend the Fellowship to a friend interested in having a big impact.

Plus, 89% of Fellows feel both more confident in their ability to make a positive impact and more ready to take ambitious actions as a result of participating.

Apply Now

Course overview

- How to 10x your impact by choosing causes carefully
- The formula of truth: Bayes’ theorem
- Scope insensitivity and the moral menace of neglecting numbers
Example resources:
🎥 YouTube video by 3Blue1Brown: “Bayes theorem, the geometry of changing beliefs”
📑 Blog post by Animal Ethics: “Scope insensitivity: failing to appreciate the numbers of those who need our help”
📚 Book by William MacAskill: Doing Good Better: Effective altruism and how you can make a difference
- Quantifying the scope and scale of global issues
- Expected value and probability theory: betting on big outcomes
- How to quantify anything with Fermi estimates
Example resources:
📊 Interactive charts by Our World in Data: “Causes of Death”
💬 Interview with Hilary Greaves: “Expected value theory”
📝 LessWrong forum post by Luke Muehlhauser: “Fermi Estimates”
- What’s the price of a human life? Financial models with real consequences
- Counting neurons and other methods for weighing welfare across species
- Predictions from the precipice: Climate modelling
Example resources:
📢 Media Release by the University of York: “The NHS is paying too much for new drugs”
📝 Forum post by Adam Shriver: “Why Neuron Counts Shouldn't Be Used as Proxies for Moral Weight”
🎦 YouTube video by metaRising: “Dystopian Futures of Astronomical Suffering”
- Machine learning and AI: maths at the forefront of emerging tech
- Mathematical modelling for pandemic preparedness and battling biorisk
- Mistakes in the moral mathematics of existential risk
Example resources:
🎥 YouTube video by 80,000 Hours: “Could AI wipe out humanity?”
📚 Book by Toby Ord: The Precipice: Existential Risk and the Future of Humanity
🎙️ Critiques of Effective Altruism podcast episode: “Astronomical Value, Existential Risk, and Billionaire Philanthropy with David Thorstad”
- Degrees and careers that capitalise on your strengths
- Statistics in social science
- Finance & quant trading: Multiply your income to maximise your impact?
Example resources:
🎧 Readout of an article by 80,000 Hours: “How to find the right career for you”
📑 Directory by Leaf: “Different potentially impactful career pathways, organised by degree subjects”
📝 Forum post by AGB: “10 years of Earning to Give”

Weekly structure

Dive deep into intriguing mathematical topics and advanced concepts using our curated resources, organised on our online learning platform with interactive videos, engaging quizzes, and other activities.
Weekly discussion with a Leaf facilitator and small-group breakouts to develop your critical thinking in conversation with intelligent, interesting, like-minded teens.
We’ll do our best to find a slot that works around your other commitments!
Get stuck into brain teasers and exercises that grapple with real-world issues. Get feedback and support from staff and peers.
Meet professionals who studied mathematics and are using what they learned to change the world.
Share your own knowledge plus join sessions run by Fellows and alumni! Meet inspiring peers with shared interests; collaborate on projects; discover exciting new ideas.
Discord channel, paired 1:1s, and opportunities to get to know peers with different backgrounds but shared passions.
Find study buddies and indulge in your mathematical hobbies — competitive or casual, impactful, impressive, or just intrinsically enjoyable!

Meet the staff and prior speakers

Leaf is supported by a wide range of experts, facilitators, and alumni to help support the growth of our Fellows.

Spencer Greenberg

Mathematician and entrepreneur

Spencer is an entrepreneur with a focus on improving human well-being. He's the founder of ClearerThinking.org, which provides 80 free, digital tools to help people make better decisions and improve their lives, as well as the host of the Clearer Thinking podcast. Spencer is also the founder of Spark Wave. Spencer's work has been featured by numerous major media outlets, including The Wall Street Journal, the Independent, the New York Times, Lifehacker, Gizmodo, Fast Company, and the Financial Times. He has a Ph.D. in applied math from New York University, with a specialty in machine learning.

Sanjay Joshi

Finance, ESG, and charity founder

Sanjay is a seasoned actuary and entrepreneur with a background in finance, financial analysis, and charity impact. He founded SoGive (charity data and analysis), Finsimco (innovative financial education), Pandemic Prevention Network (self-explanatory!) and Talk It Over Chatbot (applying AI to help people who are feeling low). He is also an Impact and ESG specialist at the investment consultancy Hymans Robertson. He studied mathematics at Cambridge University.

Annabella Wheatley

Oxford Biosecurity Group

Annabella achieved undergraduate and master’s degrees in Materials Science, both from the University of Oxford, and was a committee member of Effective Altruism Oxford while studying there. She is currently a researcher at the Oxford Biosecurity Group, exploring the potential of Far UVC lighting for killing pathogens and eliminating pandemic threats. She has been teaching and tutoring maths and science for six years.

Noah Siegel

Google DeepMind

Noah is a Research Engineer at Google DeepMind. After his research at the Allen Institute for AI in Seattle, he worked on machine learning for robotics at DeepMind before switching to focus on language model reasoning and explanations as part of AI Safety and alignment research. Having studied computer science, economics, and maths as an undergraduate, he is now pursuing a PhD in Artificial Intelligence at University College London via the UCL-DeepMind joint PhD program.

Vicky Cox

Charity Entrepreneurship

Vicky is a Research and Operations Analyst at Charity Entrepreneurship, which launches high-impact nonprofits by connecting entrepreneurs with effective ideas, training, and funding. She joined their incubation programme herself shortly after graduating from her degree in mathematics and actuarial science at the University of Southampton, but decided to stay on at CE rather than set up a new charity herself.

Jonah Boucher

Course designer and facilitator

Harvard Graduate School of Education

Jonah is a teacher and curriculum designer in the US. He has supported and led projects to help talented and passionate high school and college students lead impactful and fulfilling lives. Jonah recently graduated from the Harvard Graduate School of Education and previously came first in his class (of over 500) at Hamilton College with degrees in Mathematics and Environmental Science.

Jessica Wen

High Impact Engineers

Jessica graduated from Oxford University in 2021 with an MEng in Materials Science and worked as a mechanical engineer at a global automotive company in the UK before running High Impact Engineers full-time, increasing the quantity of impactful work done by physical engineers across the globe.

Alexander Barry

A/B Statistical Consulting

Alexander is a statistical consultant who works with organisations to help them get the most out of their data, especially impact-focused non-profits. He has a masters in statistics from the University of Oxford, and did his undergrad in mathematics at Cambridge. Recently he worked with the careers advice organisation 80,000 Hours to help them assess the cost effectiveness of their digital outreach.

Jenny Zhan

University of Cambridge

Jenny is a first-year Mathematics Student at the University of Cambridge. She is currently attending seminars on ethics in mathematics and supporting Effective Altruism Cambridge as a committee member. She is an alumnus of Leaf’s 2023 Changemakers Fellowship, the Non-Trivial Fellowship, and a Global Challenges Project workshop on existential risk. Jenny enjoys cybersecurity competitions and beta testing software.

The opportunities don’t end after 5 weeks

Alumni from our recent 2024 programmes are being supported to pursue projects like:

Research into topics they were fascinated by during the course content
An international youth debate organization focusing on high-impact topics
A new fundraising initiative, Youth United for Good, coordinating an inter-school non-uniform day to raise money for GiveWell-recommended cost-effective charities

Our August Fellows programme supports top Finalists with additional next steps

Up to £1,000 in grant funding plus mentorship for projects

Group accountability calls and an ongoing peer network
Referrals to and application support for partner programmes
Virtual work experiences with a high-impact nonprofit

*These follow-ups are applied for or earned during the Finalist June/July cohort, not guaranteed!

Plus, all Finalists will still have access to the online learning platform, the Discord channel, and your new friends after the five weeks end.

Alumni have gone on to work with:

Alumni perspectives

"This program transformed my view on how to maximise and actually quantify impact. As well as the main content created by Leaf, there were interesting websites and links throughout; GiveWell was my personal favourite, and 80,000 hours was also very interesting, particularly their ranking of the world's most pressing problems. Live sessions were my favourite part; my facilitator Jenny was not only very fun but also taught us a lot. Furthermore, being with the other students was enjoyable and helpful, as we often bounced off each other and it stimulated very fun and thought-provoking discussion."

Baqir
"Leaf has made me want to dedicate my career to make more meaningful change in the world, rather that just aimlessly wander into academic research. Nothing’s set in stone, but I'm considering becoming a researcher focusing on ways to combat existential risk and climate change. Leaf has definitely changed my approach to using my money and time in the most effective ways. The fellowship has a lot of useful information about how to make a larger impact, as well as opportunities to make connections that would make it easier to do so in the future. I really liked the weekly discussion calls, problem sheets, and Discord."

Rachel
"Perhaps the most valuable thing I've learned is that a traditional subject like maths, where its applications are mainly believed to be finance and banking, can be so important and conducive to many other professions and careers in many practical ways! I've acquired so much knowledge and exposure to different career pathways and positions. Also, before Leaf, I was very much of the opinion that the most commonly-discussed problems were the most important; now, I recognise that there are many world and wide-scale issues which are solvable yet neglected, such as legislation for AI use regarding its risks, or even space governance."

Joseph
"I learned lots about the unreliable intuition of humans regarding statistics and numbers in general, and that there are many ways of dealing with these inaccuracies. I was also exposed to a variety of tools and philosophies used in the world of effective altruism, like longtermism, QALYs, and utilitarianism. Although each has its flaws, I believe that these ways of thinking or modelling various issues can help us to improve our decision-making. This summer, I'll be creating a climate model to predict surface warming of Chad in the next 100 years; this project idea stemmed out of The Mathematics of Morality."

Oliver
"It was a good way of combining a subject that I'm interested in with exploring world problems. I found the actual application of mathematics in the real world very helpful in understanding the scale of different problems and also the ethical issues of quantifying certain areas such as lives. I think the mathematical concepts were very valuable such as Fermi estimates and the discussion about Bayes' Theorem. I liked the weekly discussions in general and hearing other people's ideas about morality and its links to mathematics. I particularly enjoyed talking about the trolley problem."

Ashima
"I really enjoyed the different concepts and mathematical skills we learned, as I have never used maths like this before! I feel like this programme has really widened my thinking and given me new approaches to solving problems. I really enjoyed some of the discussions we had in our group calls around AI and neuron counts. The idea of 'scope insensitivity' was particularly useful as I had no idea about how serious an issue it was. The ideas on giving effectively were also helpful; I still plan to do engineering but I will now have a stronger focus on thinking about the good my career is doing and the ethics of the company I work for."

Freya
"The network that Leaf creates is full of inspiring people with inspiring goals. I wanted to work with financial statistics; Leaf didn't change my career plans but my perspective on what I should do with my income. I found the ideas about effective altruism particularly useful, exploring how a pound donated has varying value depending on who is the receiving the money. It was valuable to learn how a career in finance or statistics can still have a positive impact if you pledge to donate your money to effective causes."

Elliot