For extremists, there can be no end to the opposition, except the destruction of the other group within the jurisdiction the extremists' control. In contrast, extremists believe the 'other' must always be opposed, controlled or destroyed because its intrinsic nature and existence is inimical to the success of the extremists’ own group. The unconditional nature of the opposition is key to this definition most normal conflicts (even violent ones) can be resolved in some manner that accommodates both parties, such as a fight that ends with a handshake, or a war that ends with a treaty. What are extremism’s defining characteristics? If the ideology that justified slavery is thus related to modern white supremacist beliefs, which most people agree are extremist, then isn’t slavery also a form of extremism? Shouldn’t we study both as part of a single category? In my book, Extremism, I argue that this phenomenon is better understood as a product of group dynamics – the belief that one’s own group cannot succeed or survive unless it is constantly and unconditionally set in opposition to another group.