Ralph tries to make Jack see sense by showing him the conch which had been the symbol of leadership and also, friendship.

see 在这里不是字面的"看见"，而是"理解、明白"的意思。 sense 指"理智、判断力"，常用来表示对事物的合理认知或正确理解。 see sense 是一个固定短语，意思是"醒悟过来、明白事理"，指某人从不理智的状态转变为理智的状态。