"人类的正当研究对象是人类"

Simplified Meaning:

Understanding people is very important for anyone who wants to learn about humans. For example, think about a doctor. Before they can treat patients, they need to learn a lot about the human body and how it works. In the same way, anyone who wants to understand human behavior, emotions, and society should study people closely. Another example is a teacher who spends time getting to know their students. By understanding each student's needs and personality, the teacher can help them learn better. So, if you want to do well in any field involving people, like business, teaching, or counseling, pay attention to human nature. Knowing how people think and act helps you relate to them better and can lead to success in your work.