This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book discusses antisemitism in social spaces which think of themselves as antiracist and democratic. It also discusses antisemitism amongst people who believe that they strongly oppose antisemitism. The book explains the antisemitism to be found within that part of the elite which thinks of itself as progressive. It attempts to understand a complex and contradictory reality, a world in which people's self-consciousness comes into conflict with the ways in which other people interpret them and their actions. The book argues that a 'politics of position' is emerging on the left in preference to a politics of reason or persuasion. It looks at radical critiques of Israel and Zionism with a focus on how they tend to free themselves from empirical, rational or comparative methodological constraints.