Such is the aim of the work I have undertaken, and its result will be to show by appeal to reason and fact that nature has set no term to the perfection of human faculties; that the perfectibility of man is truly indefinite; and that the progress of this perfectibility... has no other limit than the duration of the globe upon which nature has cast us. This progress will doubtless vary in speed, but it will never be reversed as long as the earth occupies its present place in the system of the universe and as long as the general laws of this system produce neither a general cataclysm nor such changes as will deprive the human race of its present faculties and its present resources....
After long periods of error, after being led astray by vague or incomplete theories, publicists have at last discovered the true rights of man and how they can all be deduced from the single truth, that man is a sentient being, capable of reasoning and of acquiring moral ideas....
At last man could proclaim aloud his right, which for so long had been ignored, to submit all opinions to his own reason and to use in the search for truth the only instrument for its recognition that he has been given.
Force or persuasion on the part of governments, priestly intolerance, and even national prejudices, had all lost their deadly power to smother the voice of truth, and nothing could now protect the enemies of reason or the oppressors of freedom from a sentence to which the whole of Europe would soon subscribe....
Our hopes for the future condition of the human race can be subsumed under three heads: the abolition of inequality between nations, the progress of equality within each nation, and the true perfection of mankind. Will all nations one day attain that state of civilization which the most enlightened, the freest and least burdened by prejudices, such as the French and the Anglo-Americans, have attained already? Will the vast gulf that separates these people from the slavery of nations under the rule of monarchs, from the barbarism of African tribes, from the ignorance of savages, little by little disappear?
The time will therefore come when the sun will shine only on free men who know no other master but their reason; when tyrants and slaves, priests and their stupid or hypocritical instruments will exist only in works of history and on the stage; and when we shall think of them only to pity their victims and their dupes; to maintain ourselves in a state of vigilance by thinking of their excesses; and to learn how to recognize and so to destroy, by force of reason, the first seeds of tyranny and superstition, should they ever dare to reappear amongst us.