The term 'with a sound mind' can be summarized with two crossword solutions: SANE (4 letters) and LUCIDLY (7 letters). SANE is an adjective meaning 'mentally sound, rational, and HEALTHY'. It is derived from the Latin word sanus, which means 'HEALTHY'. LUCIDLY is an adverb meaning 'clearly and intelligently'. It is derived from the Latin word lucidus, which means 'bright or shining'. Together, these two words describe someone who is mentally sound and able to think clearly.