Principia Ethica, written in 1903, was a groundbreaking work of moral philosophy. Its author, G.E. Moore, questioned a fundamental pillar of ethics—specifically, what the definition of 'good' is. As influential now as it was in its own time-period, Principia Ethica represented an advance in human thinking and is a worthy work for current and future generations to study to gain a better understanding of values and ethics.