To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge. Read Summary
For I am not so enamoured of my own opinions that I disregard what others may think of them. Read Summary
Mathematics is written for mathematicians. Read Summary
So far as hypotheses are concerned, let no one expect anything certain from astronomy, which cannot furnish it, lest he accept as the truth ideas conceived for another purpose, and depart from this study a greater fool than when he entered it. Read Summary
I am aware that a philosopher's ideas are not subject to the judgment of ordinary persons, because it is his endeavour to seek the truth in all things, to the extent permitted to human reason by God. Read Summary
Accordingly, since nothing prevents the earth from moving, I suggest that we should now consider also whether several motions suit it, so that it can be regarded as one of the planets. For, it is not the center of all the revolutions. Read Summary
First of all, we must note that the universe is spherical. Read Summary
The earth also is spherical, since it presses upon its center from every direction. Read Summary
Those who know that the consensus of many centuries has sanctioned the conception that the earth remains at rest in the middle of the heavens as its center, would, I reflected, regard it as an insane pronouncement if I made the opposite assertion that the earth moves. Read Summary
The massive bulk of the earth does indeed shrink to insignificance in comparison with the size of the heavens. Read Summary
We regard it as a certainty that the earth, enclosed between poles, is bounded by a spherical surface. Read Summary
Of all things visible, the highest is the heaven of the fixed stars. Read Summary
Those things which I am saying now may be obscure, yet they will be made clearer in their proper place. Read Summary
I can easily conceive, most Holy Father, that as soon as some people learn that in this book which I have written concerning the revolutions of the heavenly bodies, I ascribe certain motions to the Earth, they will cry out at once that I and my theory should be rejected. Read Summary
Therefore, when I considered this carefully, the contempt which I had to fear because of the novelty and apparent absurdity of my view, nearly induced me to abandon utterly the work I had begun. Read Summary
Moreover, since the sun remains stationary, whatever appears as a motion of the sun is really due rather to the motion of the earth. Read Summary
Yet if anyone believes that the earth rotates, surely he will hold that its motion is natural, not violent. Read Summary
Near the sun is the center of the universe. Read Summary
Pouring forth its seas everywhere, then, the ocean envelops the earth and fills its deeper chasms. Read Summary
Therefore, in the course of the work I have followed this plan: I describe in the first book all the positions of the orbits together with the movements which I ascribe to the Earth, in order that this book might contain, as it were, the general scheme of the universe. Read Summary