Even great spirits have only their five-fingers' breadth of experience - just beyond it their thinking ceases and their endless empty space and stupidity begins.
Thoughts without content are empty, intuitions without concepts are blind... The understanding can intuit nothing, the senses can think nothing. Only through their union can knowledge arise.
For knowing is spoken of in three ways: it may be either universal knowledge or knowledge proper to the matter in hand or actualising such knowledge; consequently three kinds of error also are possible.
To realize that our knowledge is ignorance, This is a noble insight. To regard our ignorance as knowledge, This is mental sickness. Only when we are sick of the sickness Shall we cease to be sick. The Sage is not sick, being sick of sickness; This is the secret of health.