Let man then contemplate nature in full and lofty majesty, and turn his eyes away from the mean objects which surround him. Let him look at the dazzling light hung aloft as an eternal lamp to lighten the universe; let him behold the earth, a mere dot compared with the vast circuit which that orb describes, and stand amazed to find that the vast circuit itself is but a very fine point compared with the orbit traced by the starts as they roll their course on high.

You see, if the height of the mercury [barometer] column is less on the top of a mountain than at the foot of it (as I have many reasons for believing, although everyone who has so far written about it is of the contrary opinion), it follows that the weight of the air must be the sole cause of the phenomenon, and not that abhorrence of a vacuum, since it is obvious that at the foot of the mountain there is more air to have weight than at the summit, and we cannot possibly say that the air at the foot of the mountain has a greater aversion to empty space than at the top.

Orthodoxy on one side of the Pyrenees may be heresy on the other.

Those who are accustomed to judge by feeling do not understand the process of reasoning, because they want to comprehend at a glance and are not used to seeking for first principles. Those, on the other hand, who are accustomed to reason from first principles do not understand matters of feeling at all, because they look for first principles and are unable to comprehend at a glance.

Discourses on humility are a source of pride in the vain and of humility in the humble.

Piety is different from superstition. To carry piety to the extent of superstition is to destroy it. The heretics reproach us with this superstitious submission. It is doing what they reproach us with.

The truth about nature we discover with our brains. The truth about religion we discover with our hearts.