Harvard Book Store and Oxfam America presented acclaimed ethicist **Peter Singer** for a discussion of his latest book, _The Most Good You Can Do: How Effective Altruism Is Changing Ideas About Living Ethically._ Peter Singer’s books and ideas have been disturbing our complacency ever since the appearance of _Animal Liberation_. Now he directs our attention to a new movement in which his own ideas have played a crucial role: effective altruism. This movement is built upon the simple but profound idea that living a fully ethical life involves doing the "most good you can do." Such a life requires an unsentimental view of charitable giving: to be a worthy recipient of our support, an organization must be able to demonstrate that it will do more good with our money or our time than other options open to us. Singer introduces us to an array of remarkable people who are restructuring their lives in accordance with these ideas, and shows how living altruistically often leads to greater personal fulfillment than living for oneself.