Staring at the symptoms displayed by a patient, a doctor would generally be able to predict the disease the patient is suffering from. And the more experienced the doctor is, the more accurate their prediction would be.
Because, they would be able to refer to this experience—having witnessed people with similar symptoms. And based on it, they would be able to infer the information and even tell diseases—with similar symptoms—apart.
An experienced farmer would only need to glance at the farm to know whether the soil condition was fit to grow a healthy field of crops. By observing his surroundings, staring at the clouds, the temperature and moisture content in the wind, and the behaviour of ants and other insects, he would be able to tell whether it was about to rain or not.
