“Nadir” can be a specific medical term that indicates the “minimum value of a fluctuating quantity” or an astronomical term that describes either “a point on the celestial sphere diametrically opposite some other point” or “the point on the celestial sphere diametrically opposite to the zenith and directly below the observer” (_Oxford Universal Dictionary_ 1955). Yet “nadir” is perhaps most frequently used as an antonym for the more general sense of “zenith,” or “high point.” Put another way, “nadir” indicates the lowest point possible for a person or collective; it can identify the very worst moment of a particular era or situation as well. The English historian Henry Hallam (1777–­1859) used the term “nadir” during the early nineteenth century to refer to what he considered a particularly abysmal period in human history. In the first volume of _Introduction to the Literature of Europe, in the Fifteenth, Sixteenth, and Seventeenth Centuries_, Hallam bluntly referred to the “seventh century [as]... the _nadir_ of the human mind in Europe” ([1837] 1876, 4). Hallam might have drawn from a 1793 definition of “nadir” as “the place or time of greatest depression or degradation” in making such an assertion (_Oxford University Dictionary_ 1955). Over one...