Why can the doctor see the patient's condition from the X-ray?

If the doctor is given an X-ray of the human brain, what can he find through observation? He can discover subtle secrets of the brain, such as that this part is completely normal, that part shows signs of pathological changes, that part has shrunk, and there are basic functions.

If you are a primary school student, you may only see a gray-black image. Maybe you are good at biology class, knowing that the image on the X-ray shows the human brain.

If you are a junior medical student, you may be able to read more information from the film: left and right hemispheres, undulating sulcus, posterior cerebellum and so on.

For doctors, their professional knowledge and work experience "guide" his eyes to observe X-rays, so as to find out the problem. Therefore, for a theoretically prepared observer, the observed object will show rich content; For an observer who is not fully prepared in theory, the object of observation may be just an image.

According to the British philosopher Popper, theory precedes observation. It means pure observation without purpose is just "looking". For example, I look at every car that passes in front of me. Because my observation has no purpose and method, I just "see" a car passing by. If I take a task to observe, for example, the license plate number of a car, I will find that there are three symbols on the license plate of all cars: a Chinese character representing the abbreviation of the province, several capitalized English letters and several Arabic numerals.

Or I am an automobile engineer, and I can get a series of data through a device pre-installed on the road where the car is driving. By analyzing these data, I can know which cars have good performance and which need to be repaired in time, which is the same as the reason why doctors look at X-rays.

Summary: Popper's viewpoint tells us that scientific observation is conducted under the guidance of theory, and it is not a blind and random activity.

From another angle, it also tells us that a law or theory can be discovered or created because human reason has observed and known nature in advance according to its own intention, which is what Kant said, "human reason legislates for nature." It is through these theoretical observation activities that people have more understanding and grasp of nature.