G. E. Moore 
Principia Ethica [EPUB ebook] 

First published in 1903, this volume revolutionized philosophy and forever altered the direction of ethical studies. It clarifies some of moral philosophy’s most common confusions and redefines the science’s terminology. 6 chapters explore: the subject matter of ethics, naturalistic ethics, hedonism, metaphysical ethics, ethics in relation to conduct, and the ideal.