{ 1 } - comes from sense experience.
{ 2 } - comes from inner reason.
{ 3 } - is impossible for humans.

True knowledge is from within, from reason. We reach it by questioning and by reminiscence.

Geometry is model of true knowledge. The slave in the Meno reached a geometrical theorem as the result of questioning, even though he had never studied geometry before.

Plato wrote dialogues -- which themselves featured questioning as the way to gain knowledge.