There are three levels of truth :
Experience, reasoning, and knowing.
All other assertions should be rejected.
The first type of truth is experience. Once you have experienced something, you know it. No person can persuade you otherwise.
The second type is truth gained by reasoning. In this case, the truth cannot be immediately verified because the subject is too small (like atomic particles) or too large (like the movement of planets through time) or too abstract (like ideas). Something may be true, but its truth is borne out by analysis rather than physical testing.
Either of these two types of truths has a range of validity. They are relative. Therefore, though truths are superior to falsehood, opinions, beliefs, and superstition, they each have limits. There is a third type of truth that is different from these two.
This is a way of direct spiritual knowing. Wholly internal, this mode is the direct experiencing of truth through the opening of higher faculties. Meditation gives one perceptions of absolute certainty. There is no doubt or need of other investigations; this knowledge is beyond words, descriptions, and rationalization. In fact, one must be careful not to let the fruits of one’s meditations pass into the realm of rationalization. This will subject you to the relativity of external truths and ruin your confidence. To avoid doubts and conflicting opinions, followers of Tao keep their revelations secret. Then what is known directly is absolutely yours.