Latin for “sound/healthy mind.” Mr. Walker uses this Latin phrase in reference to Mr. Crawley’s questionable madness. Mr. Walker says to Mr. Robarts that Mr. Crawley’s trial can be postponed if he is found to be not mentally sound. Perhaps this Latin phrase euphemistically implies Mr. Crawley’s propensity for mentally unhealthy behavior without outright stating that he is mad. Mr. Walker could be using this Latin euphemism and not bluntly stating that Mr. Crawley is mad because he regards Mr. Crawley as a gentleman and such a description is not appropriate for a gentleman. The phrase is attributed to the Roman poet Juvenal who wrote the famous phrase mens sana in corpore sano or “a healthy mind in a healthy body.” [AM 2006]
Sources: Juvenal, Satire 10.356.