Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.
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.
To know how little one knows is to have genuine knowledge. Not to know how little one knows is to be deluded. Only those who know when they are deluded can free themselves from such delusion. The intelligent people are not deluded, because they know and accept their ignorance as ignorance, and thereby have genuine knowledge.
For the purpose of knowledge we must know how to make use of the inward current which draws us towards a thing, and also of the current which after a time draws us away from it.
What we know is not capable of being otherwise; of things capable of being otherwise we do not know, when they have passed outsideour observation, whether they exist or not. Therefore the object of knowledge is of necessity. Therefore it is eternal; for things that are of necessity in the unqualified sense are all eternal; and things that are eternal are ungenerated and imperishable.
Knowing things halfway is a greater success than knowing things completely: it takes things to be simpler than they really are andso makes its opinions more easily understandable and persuasive.
But this is that which will dignify and exalt knowledge: if contemplation and action be more nearly and straitly conjoined and united together than they have been: a conjunction like unto that of the highest planets, Saturn, the planet of rest and contemplation, and Jupiter, the planet of civil society and action.