Effective altruism is a philosophy that uses evidence and reason to determine the most impactful ways to improve the world. It aims to allow people to give charitably with both heart and head. For example, it costs $50,000 to train a seeing eye dog but only $20 to treat a disease that could cure blindness for 30 years in developing countries, demonstrating how effective altruism can have over 10,000 times the impact of other charities.