Single-heartedness

Just as Augustine notes that a true virgin must be a virgin physically and spiritually, so too a monk's single-heartedness of purpose in Christ cannot be left to an ethereal realm.

Source: wiktionary

...the result of which congress was an unanimous declaration of their forgiveness of a piece of thoughtless levity on the part of the giddy girl ; and every allowance being pleaded for her single-heartedness and ingenuousness, it was determined that no allusion whatever should again be made to the disagreeable subject;

Source: wiktionary