The aim of this book is to prove that pollution was an important concept in Roman religion. The subject is difficult because of the slippery nature of Latin vocabulary on pollution: we have plenty of verbs and adjectives to describe processes and statuses of defilement or purification, but a surprising lack of relevant abstract nouns. In a sense, Lennon aims at producing a Roman counterpart to Robert Parker's monograph on pollution in Greek religion (Miasma: Pollution and Purification in Early Greek Religion (1983)). L. also wants to take account of anthropological theories of pollution and to expand arguments on the connection between the body and the city developed by Holt Parker on Vestals (AJPh 125 (2004), 563–601).

The book consists of five chapters, introduction and conclusions. The introduction sets out the aims and structure of the work and its place in relation to other scholarship. The aim of the first chapter is to define the Latin vocabulary of pollution. Some emphasis is put on the nouns nefas and scelus. It is also argued that profanus and sacer have some connection with pollution. A further section of the chapter analyses the ways in which religion was connected with pollution and purification: temples and, to a certain extent, the pomerium represented spaces which had to be kept clean from sources of impurity, especially bloodshed. Chs 2–4 are structured phenomenologically and each is dedicated to a possible form of pollution. Ch. 2 explores defilement connected to sexually related activity. First, birth and abstinence are analysed. Prostitutes and menstrual blood both seem to have been considered major causes of pollution. Ch. 3 considers bloodshed. Homicide was not necessarily considered polluting, whereas parricide would have had strongly defiling consequences. Ceremonial killings tended to be without bloodshed. Outside military contexts, human blood inspired revulsion and was associated with cannibalism. During wars, on the other hand, blood was not a cause of pollution. A significant exception is civil war, where blood was seen as polluting. Ch. 4 is dedicated to pollution coming from death. Ancient texts describe the presence of a corpse in the house as unequivocally polluting. L. argues that undertakers, executioners and gladiators were reviled because of their continuous contact with death. Finally, the author looks at the evidence on Roman festivals in which the several types of spirits of the dead could come in contact with the living. L. insists that, although these festivals are not openly described in terms of pollution, they all required rituals of purification. Ch. 5 brings the threads together, demonstrating that in De domo sua Cicero heavily used a rhetoric of pollution in relation to Clodius and his dedication to Libertas.

This is certainly a courageous book, which must be welcome as the first monograph attempting a broad analysis of what is undoubtedly a very difficult topic of study. L.'s closing words are ‘pollution mattered’ (196), and this is an assertion that he convincingly demonstrates, providing food for thought and a stimulating challenge to all scholars working on the history of religions in ancient Rome and Italy. The author's mastery of classical and anthropological scholarship on pollution is admirable. His skills as a classicist are very sound, as shown by his brilliant reading of De domo sua.

I have two reservations, one of which is directed not at anything the book says, but rather at the fact that on some topics it does not say enough. The first chapter in particular, which has an essential organizing function in defining the Latin concepts which are used in the rest of the book, could and should have been significantly expanded. L.'s aim is not to provide a comprehensive study of this vocabulary, but nuanced and complex concepts such as profanus and sacer clearly deserve more discussion. The chapter is far too brief, and this results in the exclusion of significant evidence. On profanus, for example, L. does not take into account the formula of slaves’ manumission transmitted by Festus, connecting purus, probus and profanus (296 L). One of the main pieces of evidence that L. uses to argue that scelus and pollution were closely connected is a passage of the Differentiae verborum attributed to Suetonius, in which sceleratus is glossed as contaminatus vel aliqua contagione pollutus (289 Reifferscheid). This attribution, however, has been seriously questioned (G. Brugnoli, Studi sulle Differentiae verborum (1955), 61–94). Servius (Aen. 3.42) also glosses scelerare as polluere, and this may point to a later date for the close association between the terms. The second point is closely connected to the first and regards the semantic field of sacrum. L.'s interpretation of sacer is clearly influenced by the outdated theory of sacer as ‘separated’, which has been advanced in various forms from Otto to Eliade and Dumézil, and does not consider the fundamental monograph of Claudia Santi (Alle radici del sacro (2004)), who has convincingly redefined sacer and sacrum in terms of a relationship between the civic community, the gods and the underworld. This is of some consequence for the whole book, as the author uses the separation theory in many of his interpretations.

In conclusion, this is a book to be warmly recommended to anyone working on the religious history of ancient Italy. It provides many refreshing insights and draws attention to a neglected and important topic. I sincerely hope that it will open the way to further research.