阅读下例短文.简要回答问题。
Thinking is something you choose to do as a fish chooses to live in water. To be human is to think. But thinking may come naturally without your knowing'how you do it. Thinking about drinking is the key to critical (判断性的) thinking. When you think critically, you take control of your thinking processes (过程) . Otherwise, you might be controlled by the ideas of others. Indeed, critical thinking is at the heart of education.