6 ideas
Condorcet argues that the improvement of human faculties is indefinite: it can slow down, but no natural boundary caps it. Progress depends only on how long the earth lasts and on the general laws of the universe, not on any fixed ceiling in human nature.
Treat history as the record of how knowledge is gained, spread and applied, not as a chronicle of dynasties and wars. Epochs are defined by changes in cognitive tools such as language, agriculture, writing and printing. Seeing it this way makes intellectual technologies the true turning points of human affairs.
Once writing and specialized learning appear, a caste of priests or scholars hoards knowledge and keeps a 'double doctrine': truth for themselves and superstition for the masses. This deliberate information asymmetry turns knowledge into an instrument of domination, and it makes public diffusion of learning a political act of liberation.
Before printing, knowledge lived in few copies and could be destroyed or suppressed, so civilizations could regress. Printing multiplied texts cheaply and put ideas beyond any authority's power to erase, creating an independent public opinion. Because accumulated truth can no longer be wholly lost, backsliding into general ignorance becomes nearly impossible.
Condorcet predicts the future along three axes: ending inequality between nations, reducing inequality within each nation, and truly perfecting individual humans. Within nations, he names three sources of inequality to target: unequal wealth, unequal security of livelihood (addressed by social insurance), and unequal education. Each can be reduced through public instruction, better institutions and the application of probability to social questions.
Condorcet wrote the Sketch while hiding from Robespierre's Terror, after being proscribed by the revolution he had championed. He died in prison soon after his arrest in 1794. His confident forecast of reason's triumph, written while the revolution was consuming its own philosophers, shows that faith in long-run progress can survive the collapse of one's own hopes.