synthesis即主题升华。
所谓主题升华，就是通过让主题事件和其他地区或时期的历史事件进行比较、关联而产生新洞见，进一步升华和延伸论证，使你的立场和论证更有深度。
写作技巧：要学会像美国人一样对历史进行思考。这是进行主题升华的基础，也会从根本上提高你AP历史论文的质量。你可以开始练习主动地思考事物间的因果关系，在阅读教材、记忆史实的时候问自己：
1、 What happened?
2、 Why did the event happen? What were the reasons? What was the context?
3、 Why does the event matter? what are the consequences?
4、 Does the event make you think of other similar/related events?
5、 How are they similar?
6、 In what ways do they differ?
