Flaubert isn't arguing for relativism or suggesting that facts don't exist—he's warning against the writer's (and by extension, anyone's) tendency to mistake their carefully constructed version of events for reality itself. The novelist knows better than most that selection, emphasis, and omission shape what we present as truth, and that our perceptions, however sincere, are always mediated through our particular vantage point. When you argue passionately with someone who witnessed the same event but saw something entirely different, you're both likely clinging to perception while calling it truth—neither of you lying, yet neither of you seeing the whole. Flaubert's insight asks us to hold our certainties more lightly, recognizing that intellectual honesty requires acknowledging the gap between what we've perceived and what actually occurred.