Originally from Ancient Greek ἐνθουσιασμός (the god within), transliterated at the end of the 16th century into French enthousiasme and finally into English. The book reports all the attestations of the word "enthusiasm" in the history of English literature. The word initially had a religious, almost fanatical connotation, with a sense of divine inspiration, not justified or explained rationally. For a certain period the concept of enthusiasm was considered an "intuition" (end) without the use of reason (means) and therefore associated with madness and irrationality. With Locke we begin to consider a more rational semantic connotation. Gradually it begins to be detached from its religious connotation. Coleridge defines enthusiasm as “vividness of ideas”.
In the second half of the book, metaphors for the word enthusiasm are reported. The ones that struck me most are: “rapid extension of natural knowledge; “excuse my enthusiasm, because I am really drunk on intellectual vision”; “ardor anima/mentis”; “a kind of spell”; fervor and ardor; “Enthousiasme, fureur poétique et puissance imaginative” (Diderot).
I found the reading certainly not light but interesting, at least from the point of view of a person who loves the concept (in the modern sense of the term, with positive connotations) to the point of tattooing the word itself.