Q From Marcus Wisbech: “Why is it that when a person is angry about something, we might say ‘He’s beside himself with rage?’ How can one be beside oneself?”
A It puzzles us today because language has changed but the idiom hasn’t.
The phrase appears first in the language a long time ago. In 1490, William Caxton, who established the first English printing press in Westminster, published a book with the title Eneydos. We know it better as The Aeneid by Virgil.
Caxton records its linguistic travels in its title: “translated oute of latyne in to frenshe, and oute of frenshe reduced in to Englysshe by me Wyllm Caxton”. This is the relevant passage, describing the grief of Dido at the departure of Aeneas. I’ll leave its rendering into modern English as an exercise for the reader:
She sawe the saylles, wyth the flote of the shippes that made good waye. Thenne byganne she, for grete distresse, to bete & smyte thre or four tymes wyth her fyste strongly ayenst her brest & to pulle her fayr heres from her hed, as mad & beside herself.”
Caxton was translating the French phrase hors de soi, outside oneself. He used beside because for him the word could mean outside of or away from. The idea was that powerful emotion had led Dido’s mind to escape her control. Her mind had got away from her and she wasn’t herself.
We use the phrase rather less now than we used to. When it appears, it is most often related to rage but it can also refer to delight, grief, amazement, excitement, horror, or any other powerful emotion.