For first of all we must prepare a Natural and Experimental History, sufficient and good; and this is the foundation of all; for we are not to imagine or suppose, but to discover, what nature does or may be made to do.
The true bounds and limitations, whereby human knowledge is confined and circumscribed,... are three: the first, that we do not so place our felicity in knowledge, as we forget our mortality: the second, that we make application of our knowledge, to give ourselves repose and contentment, and not distates or repining: the third, that we do not presume by the contemplation of Nature to attain to the mysteries of God.
We must see whether the same clock with weights will go faster at the top of a mountain or at the bottom of a mine; it is probable, if the pull of the weights decreases on the mountain and increases in the mine, that the earth has real attraction.
But the idols of the Market Place are the most troublesome of all: idols which have crept into the understanding through their alliances with words and names. For men believe that their reason governs words. But words turn and twist the understanding. This it is that has rendered philosophy and the sciences inactive. Words are mostly cut to the common fashion and draw the distinctions which are most obvious to the common understanding. Whenever an understanding of greater acuteness or more diligent observation would alter those lines to suit the true distinctions of nature, words complain.
To seek to extinguish anger utterly is but a bravery of the Stoics. We have better oracles: 'Be angry, but sin not.' 'Let not the sun go down upon your wrath.'
Another error is an impatience of doubt and haste to assertion without due and mature suspension of judgment. For the two ways of contemplation are not unlike the two ways of action commonly spoken of by the ancients; the one plain and smooth in the beginning, and in the end impassable; the other rough and troublesome in the entrance, but after a while fair and even. So it is in contemplation; if a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties.
There are two books laid before us to study, to prevent our falling into error; first, the volume of the Scriptures, which reveal the will of God; then the volume of the Creatures, which express His power.
Nevertheless if any skillful Servant of Nature shall bring force to bear on matter, and shall vex it and drive it to extremities as if with the purpose of reducing it to nothing, then will matter (since annihilation or true destruction is not possible except by the omnipotence of God) finding itself in these straits, turn and transform itself into strange shapes, passing from one change to another till it has gone through the whole circle and finished the period.