Genius, as the Introduction to this rich and engaging account usefully outlines, is a longstanding but frequently contested object of study. Its multiple etymology, its employment to refer to both attribute and individual, and the prevailing sense that it is somehow a self-evident quality, all contribute to the difficulty writers have in defining the term. Ann Jefferson quite explicitly makes no attempt to provide any such definition, or to construct any coherent theory of genius. Rather, she examines the uses to which the notion has been put across three centuries of French culture, in particular with reference to the concepts to which it has been opposed. These ‘others’ include talent, learning, madness, imposture, and taste, but the most consistent ‘other’ is the observer: the third party who is required to recognize, determine, comment upon, or even constrain genius. This book sets out to define the specific contribution of French thinkers to the genius debate, a contribution Jefferson suggests has traditionally been marginalized. The precise linguistic, literary, and sociocultural analysis with which she supports this wide-ranging exploration of intellectual history provides compelling evidence for her contention that there is value in taking into account the particular language and cultural tradition within which ideas are expressed. The study moves through a series of apparently unrelated contexts in which genius has been discussed: from eighteenth-century aesthetic philosophy, through the nineteenth-century quest for national identity, medical attempts to quantify and pathologize intellect, and the media fascination with child prodigies, to twentieth-century literary theory. Jefferson makes a virtue of what she terms this ‘discontinuity’, suggesting that it is precisely the continued freshness of genius that makes it attractive as an object of debate. Yet there are also several themes that link these disparate case studies. Time and again we encounter genius as the originality of perception that is necessary to human progress. The relationship between individual and collective genius appears in both discussions of national identity and considerations of an international, atemporal dynasty of genius. Genius as a performance relates precocious children to fraudulent adults, and plays a part in analyses of the qualities required to recognize genius in others. And there is a persistent fascination with how far genius resides in the biography or biology of an individual. Most striking of all is how frequently discussions of genius are used to position their author, or say something about the discipline within which that discussion is taking place. Hugo ostentatiously leaves a space for himself in his presentation of national genius; doctors define the objective, progressive logic of their discipline with respect to the uncontrollable spontaneity of genius/madness; and Sartre makes parallels between his own childhood and that of the prodigy that he describes. Jefferson concludes on the impossibility of ever stating precisely what genius is, but this study — which begins and ends with the idea of thinking with rather than about genius — provides more than ample proof of just how productive this impossibility can be, for scholars in so many fields.