9 ideas
Every solution creates new problems, so progress never reaches a final resting state, but all problems are in principle solvable given the right knowledge — there are no insoluble problems, only ones we don't yet know how to solve. This rejects both utopianism (a final perfect state) and pessimism (some barriers are permanent).
The idea that Earth is a benevolent life-support 'spaceship' is backwards: most of the planet and cosmos is lethal to humans, and we survive only by creating knowledge to build the conditions we need. Habitability is an achievement of knowledge, not a given of nature — so survival depends on continued problem-solving rather than conservation of a fragile balance.
All knowledge is conjectural and forever open to error-correction; there are no foundations, authorities, or final justifications that secure truth. Progress comes not from seeking certain sources of knowledge but from creating conjectures and subjecting them to relentless criticism that eliminates errors.
Humans are universal explainers: they can create any explanation that it is possible to create, because this capacity has no built-in ceiling. Once a system crosses the threshold into universality, as the alphabet did for writing and computers did for computation, small increments produce unlimited reach. So people are cosmically significant, since knowledge-bearing entities can control what happens to matter on astrophysical scales.
Plato's question 'Who should rule?' is the wrong question. The right one is how to remove bad rulers and policies without violence. Institutions should be judged by how easily they allow mistakes to be detected and undone. For this reason, electoral systems that produce clear accountability, such as plurality voting, can outperform proportional systems that are 'fairer' on paper but blur responsibility.
Static societies survive by suppressing criticism and replicating memes that disable their holders' ability to question them. Dynamic societies instead rely on memes that survive because they are useful and withstand criticism. For most of history, cultures were static and progress was imperceptible. The Enlightenment was the transition into a sustained tradition of criticism, which made rapid, open-ended progress possible.
Any physical transformation not forbidden by the laws of nature is achievable given the right knowledge. Every failure to achieve a desirable goal is therefore caused by a lack of knowledge, not by fixed limits or fate. This recasts disasters, diseases, and scarcity as unsolved problems, not permanent conditions.
The future growth of knowledge cannot be predicted, because predicting a future discovery would mean already having it. Forecasts of doom such as Malthus's therefore systematically fail: they extrapolate current knowledge and ignore the solutions people will create. Pessimism dressed up as prudence is really prophecy. Rational optimism means expecting that problems will keep arising and will keep being solvable.
An explanation is good when every detail plays a functional role, so changing any part destroys its ability to account for what it explains. The Persephone myth could explain winter just as easily with a different goddess or a different mood, so it constrains nothing. Axial tilt cannot be altered without making false predictions, such as winter arriving simultaneously in both hemispheres. That rigidity, not confirmation by evidence, is what makes an explanation worth holding.