In Philosophy, the contemplations of man do either penetrate unto God, or are circumferred to Nature, or are reflected and reverted upon himself. Out of which several inquiries there do arise three knowledges, Divine Philosophy, Natural Philosophy, and Human Philosophy or Humanity. For all things are marked and stamped with this triple character of the power of God, the difference of Nature and the use of Man.
We have no organ at all for knowledge, for truth: we know (or believe or imagine) precisely as much as may be useful in the interest of the human herd, the species: and even what is here called usefulness is in the end only a belief, something imagined and perhaps precisely that most fatal piece of stupidity by which we shall one day perish.
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.
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.
For myself, I like a universe that, includes much that is unknown and, at the same time, much that is knowable. A universe in which everything is known would be static and dull, as boring as the heaven of some weak-minded theologians. A universe that is unknowable is no fit place for a thinking being. The ideal universe for us is one very much like the universe we inhabit. And I would guess that this is not really much of a coincidence.
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.
Nobody knows how the stand of our knowledge about the atom would be without him. Personally, [Niels] Bohr is one of the amiable colleagues I have met. He utters his opinions like one perpetually groping and never like one who believes himself to be in possession of the truth.
From whatever you wish to know and measure you must take your leave, at least for a time. Only when you have left the town can yousee how high its towers rise above the houses.
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.
If the fresh facts come to our knowledge all fit themselves into the scheme, then our hypothesis may gradually become a solution. Sherlock Holmes speaking with Dr. Watson.