Isaac's research covers the period from the 6th century BCE until the 7th century CE. It deals with Greek and Roman history and with Jewish history from the 2nd century BCE onward. He has been member of a team surveying the Roman roads in Judaea/Palaestina with Moshe Fischer and Israel Roll, and of a group preparing a corpus of ancient inscriptions in all relevant languages from the region, the Corpus Inscriptionum Iudaeae/Palaestinae. His work on the imperial Roman army and imperialism traces various functions of the provincial army. It was commonly assumed that the main function of the Roman army was the defence of the frontier provinces against foreign enemies. Isaac argues that it had two different tasks, internal police functions and preparation for further expansion. Rome had an ideology of offence and expansion rather than preservation of the status quo and defence. In this connection Isaac has argued that the concept of an imperial frontier was irrelevant in Roman terms. The Empire was not a territorial concept, but one that expressed rule over peoples and cities. Another topic of this book is the question whether Rome had a “Grand strategy” as had been argued. Isaac has shown that this reflects a modern concept that could not apply to ancient reality. His book on the ideological roots of racism argues that racism must be distinguished from other forms of prejudice and stereotypes. It is a rationalization and systematization of prejudice first encountered in the 5th century BCE in Greece as a result of the development of abstract thinking in contemporary philosophy and medical science. The concept of environmental determinism was developed at this time and has been accepted as valid until very recently. It assumes that geography, climate and other external realities impose definite and unchangeable qualities, physical and mental on entire groups of people. As such it preceded social Darwinism as an attempt to rationalize group prejudice. It played a role too in imperialist ideology because it was used to distinguish between superior and inferior peoples. These concepts were taken over by Roman authors and by those who, in later times, used them for similar or related purposes. Thus Isaac argues that the history and development of racism as an ideology has roots going back to Graeco-Roman antiquity. Isaac is the author of numerous articles.; He is also member of a team working on the publication of a corpus of all ancient inscriptions from Judaea / Palestine. Since 2015 he is the Editor-in-Chief of the Israeli classics journal Scripta Classica Israelica.
Awards and recognition
In 2008, Isaac received the Israel Prize, for history.
