If I were again beginning my studies, I would follow the advice of Plato and start with mathematics.
It vexes me when they would constrain science by the authority of the Scriptures, and yet do not consider themselves bound to answer reason and experiment.
The deeper I go in considering the vanities of popular reasoning, the lighter and more foolish I find them. What greater stupidity can be imagined than that of calling jewels, silver, and gold “precious,” and earth and soil “base”?
If you could see the earth illuminated when you were in a place as dark as night, it would look to you more splendid than the moon.
The doctrine that the earth is neither the center of the universe nor immovable, but moves even with a daily rotation, is absurd, and both philosophically and theologically false, and at the least an error of faith.
Nature is relentless and unchangeable, and it is indifferent as to whether its hidden reasons and actions are understandable to man or not.
Where the senses fail us, reason must step in.
Philosophy is written in that great book which ever lies before our eyes – I mean the universe – but we cannot understand it if we do not first learn the language and grasp the symbols, in which it is written.
I do not think it is necessary to believe that the same God who has given us our senses, reason, and intelligence wished us to abandon their use, giving us by some other means the information that we could gain through them.
Facts which at first seem improbable will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty.
By denying scientific principles, one may maintain any paradox.
The Bible shows the way to go to heaven, not the way the heavens go.
To command their professors of astronomy to refute their own observations is to command them not to see what they do see and not to understand what they do understand.
It is surely harmful to souls to make it a heresy to believe what is proved.
Knowing thyself, that is the greatest wisdom.
You cannot teach a person something he does not already know, you can only bring what he does know to his awareness.
I truly believe the book of philosophy to be that which stands perpetually open before our eyes, though since it is written in characters different from those of our alphabet it cannot be read by everyone.
Nature’s great book is written in mathematics.
My dear Kepler, what would you say of the learned here, who, replete with the pertinacity of the asp, have steadfastly refused to cast a glance through the telescope? What shall we make of this? Shall we laugh, or shall we cry?
One can understand nature only when one has learned the language and the signs in which it speaks to us; but this language is mathematics and these signs are methematical figures.