There are several different levels of knowing.
1. Not knowing
2. Knowing through faith
3. Knowing through witnessing
4. Knowing through experience
This is best explained with an illustration.
Supposing there is a magical fruit that when eaten gives one the greatest pleasurable sensation one can ever experience. And suppose that this knowledge is known only to a limited few. Thus the majority of people do not know about it (Not Knowing).
Let us then suppose that there is a teacher who not only knows about it but possessed the fruit as well and a student came to him to ask him about it. The teacher told him all about the magical fruit and the magical qualities of the fruit and how pleasurable the sensation is for one who has taken a bite of it, but he does not show him the fruit nor offer the student to taste it. That student knows only through faith in the teacher’s teaching.
Suppose another student approached this same teacher and this time he not only told him everything about the fruit and its magical qualities but he also showed him the fruit by holding it in his hand. However, he does not offer this student a taste of it. Instead, he took a bite from the fruit and the student could see the experience of pleasure that the teacher felt after tasting the fruit. This student knows through witnessing the truth of the teaching.
Now supposing a third student approached this teacher but this time not only did the teacher explained everything about the magical fruit to the student and showed him the fruit, he also allowed the student to take a bite from this magical fruit so that he personally experienced the pleasurable sensation from it. This student knows through experiencing.
In learning, we always strive to achieve knowing through personal experience as this is the highest level of knowing. So it is with spiritual knowledge.