Guy De Maupassant said this quote
“ Madeleine in her turn stared at him steadily, straight into his eyes, in a profound, strange way, as if seeking to read something there, as if seeking to discover there that hidden part of a human being which can never be fathomed but may perhaps be glimpsed for a fleeting instant, in those moments of unguardedness or surrender or inattention, that are like doors left ajar onto the mysterious depths of the spirit... they stood for a few seconds, each gazing into the other's eyes, each striving to reach the impenetrable secret of the other's heart, to probe each other's thoughts to the quick. They tried, in a mute and passionate questioning, to see the other's conscience in its essential truth: the intimate struggles of two beings who, living side by side, never really know one another, who suspect and sniff around and spy on one another, but cannot plumb the miry depths of one another's soul. ”