プログレッシブ和英中辞典(第4版)の解説
ほんしん【本心】
❶〔正気〕one's senses [mind]；〔良心〕one's conscience
本心を失う
〔気が狂う〕lose [go out of] one's mind／be out of one's senses
本心に立ち返る
〔迷いがさめる，正気に戻る〕return to one's right mind
❷〔真意〕one's real intention(s)；〔心の底〕one's heart
そのようになさるあなたの本心が分からない
I can't understand your 「real intention [motive] in behaving like that.
彼が本心で言っているとは思えない
I don't think 「he is saying what he really thinks [he really means it.]
彼は本心から話しているのだろうか
Can he be speaking from his heart?
本心を明かすことはないだろう
He will never reveal his real intentions.
彼にはすまないことをしたと本心では感じている
At bottom [heart] I feel very bad about what I did to him.／What I did to him weighs on my conscience.