The good writer sees things sharply, vividly, accurately, and selectively (that is, he chooses what’s important), not necessarily because his power of observation is by nature more acute than that of other people (though by practice it becomes so), but because he cares about seeing things clearly and getting them down effectively. Partly he cares because he knows that careless seeing can undermine his project. Imagining the fictional scene imprecisely—failing to notice, for instance, the gesture that would in real life accompany some assertion by a character (the dismissive wave that takes back part of what has been said, or the clenched fist that reveals stronger emotion than the character has expressed)—the writer may be tricked into developing his situation in some way that is unconvincing. This is perhaps the chief offense in bad fiction: we sense that characters are being manipulated, forced to do things they would not really do. The bad writer may not intend to manipulate; he simply does not know what his characters would do because he has not been watching them closely enough in his mind’s eye—has not been catching the subtle emotional signals that, for the more careful writer, show where the action must go next.
