ingenuous

"Do you mean to say you didn't leave your wife for another woman?"

"Of course not."

"On your word of honour?"

I don't know why I asked for that. It was very ingenuous of me.

The apparent contradictions in his behaviour should therefore be discounted as ingenuous attempts to extricate himself from the consequences of an intellectual position which he once adopted but was never really his by intimate conviction.

[H]is Grace’s Man at his club, in company doubtless with other Men of equal social rank, talks over his master’s character and affairs with the ingenuous truthfulness which befits gentlemen who are met together in confidence.