This book examines the creation of the Antients Grand Lodge and traces the influence of Ireland and the London Irish, especially that of Laurence Dermott, the Antients' Grand Secretary, in the development of freemasonry in the second half of the 18th century. It demonstrates the relative accessibility of the Antients and contrasts this with the exclusivity of the 'Moderns'—the original Grand Lodge of England. The Antients instigated what became a six decades–long rivalry with the Moderns and pioneered fundamental changes to the social composition of freemasonry, extending formal sociability to the lower middling and working classes and creating one of the first modern friendly societies. Schism does not stand solely as an academic work but introduces the subject to a wider Masonic and non-Masonic audience and supplements dated historical works. The book contributes to the history of London and the London Irish in the long 18th century and examines the social and trade networks of the urban lower middling and working class, subjects that remain substantially unexplored. It also offers a prism through which Britain's calamitous relationship with Ireland can be examined.