Mankind have banned the Divinity from their presence; they have relegated him to a sanctuary; the walls of the temple restrict his view; he does not exist outside of it.

What has not been examined impartially has not been well examined. Skepticism is therefore the first step towards truth.

Scepticism is the first step toward truth.

All things must be examined, debated, investigated without exception and without regard for anyone's feelings... We must run roughshod over all these ancient puerilities, overturn the barriers that reason never erected, give back to the arts and sciences the liberty that is so precious to them.

The philosopher forms his principles on an infinity of particular observations. He does not confuse truth with plausibility, he takes for truth what is true, for false what is false, for doubtful what is doubtful, and probable what is probable. The philosophical spirit is thus a spirit of observation and accuracy.

A thing is not proved just because no one has ever questioned it. What has never been gone into impartially has never been properly gone into. Hence scepticism is the first step toward truth. It must be applied generally, because it is the touchstone.

Man was born to live with his fellow human beings. Separate him, isolate him, his character will go bad, a thousand ridiculous affects will invade his heart, extravagant thoughts will germinate in his brain, like thorns in an uncultivated land.