Once, a professor held a test on his students. The professor started with the following question, “Now, suppose you are going to cut trees on a hill. One of the trees has a big trunk while the other's small. Which will you cut?” The question got a quick reply, “Of course the big one! No need to consider.”

The professor smiled, “The big tree is a poplar commonly seen everywhere, while the small oneis a Korean pine. Consider again?” A second thought brought students more sense: a Korean pine is much more valuable than the poplar, so they changed their decision. “Naturally we'll cut the pine. The poplar isn't worth our effort.”Smile still remained on the professor's face. “But the pine's trunk is less straight than the poplar.” Rather puzzled¹, they became hesitated², then said, “While, we'll cut the poplar.” The professor gave more detail. “Though the poplar is straight, the trunk became empty within. Then what's your choice?”

Finally one ofthe students lost his patience and said, “Professor, you have asked a series³ of questions leading us to change our answers frequently⁴. What do you want to test after all?”

The professor's smile disappeared. He said, “Why none of you ask me for what purpose to cut thetree? Though my questions vary⁵ all the way, they are decided⁶ by one thing: your motivation to take the action. If it aims at making handicraft articles you may cut the pine; if you just want to have some firewood⁷, you'd better cut the poplar.”

文章大意：一次，一位教授对他的学生进行了一次测试。教授从以下问题开始问起：“假设现在你要去砍山上的树，其中一棵树的树干很大，另外一棵很小。那你会砍哪棵呢？”学生们很快就回答了：“肯定是最大的那棵啊！这个问题都不用考虑。”

教授笑着说：“如果大的那棵是随处可见的白杨树，而小的那棵是红松呢？再考虑一下？”学生思考片刻后有了头绪：红松比白杨珍贵多了，所以他们改变了主意。“很自然地，我们会砍红松。白杨根本不值得我们去努力。”教授还是继续微笑着，说：“但是红松的树干没有白杨的直。”学生们很疑惑，他们有点犹豫，接着说：“那我们还是会砍白杨。”教授又给了很多细节，“虽然白杨树更笔直，但是它的树干里面是空心的。你们的选择又是什么呢？”

终于有一个学生失去了耐心，他说：“老师，你问了一连串的问题来引导我们改变我们的选择，你究竟是想测试什么呢？”

这时，教授脸上的笑容消失了，他说：“为什么你们当中没有人问我砍树的目的是什么？虽然我的问题一直在改变，但是砍树始终是由一件事情来决定的：就是你采取行动的动机。如果你的目的是想要制造工艺品，那你可以砍掉红松；如果你只是想要一些柴火，那你最好把白杨树砍了。”