Off the top of my head, strong candidates for that set are:
**“#Suffering is bad”**
That's the only thing that I'm certain is bad. My foundation for #ethics.
**“#Mathematics is true”**
Math is the only #epistemology that I trust. And math is behind everything.
**“I matter. Others matter, too.”**
This guards against the polar opposites of egotism and immolation — both mistaken.
[…]
Other propositions, while true and important, are derivative, reducible — not axiomatic:
“#Wellbeing matters”
…insofar as there's (some degree of) consciousness/sentience. Because only sentient entities can suffer. And suffering is what matters.
eg, relieving a horse of a toothache is more important than preventing the annihilation of a sterile galaxy. There's no “wellbeing” in a corner of the universe where there are no conscious creatures, no matter how vast that chunk of space-time be.
(If putting “destruction of an entire galaxy” lower in your list of worries than “someone somewhere breaks his little finger” sounds alarming to you, it's only because it is extremely improbable that we could know for sure that the galaxy is entirely devoid of sentience, is incapable of developing or hosting consciousness ever in the future, and is not and will not provide shelter or resources to any creature. Very little confidence in that, therefore too much risk in prioritising a toothache over the fate of a billion stars in practice.)
“#Pleasure is good”
This is true only because (or to the extent that) pleasure is incompatible with suffering, or that pleasure means that whatever the level of suffering it is being offset by a greater amount of the opposite stuff.
“#Freedom matters”
Very often more freedom means individuals accomplish more of their stated preferences, and very often those preferences point towards less suffering for them (and sometimes for others, too).
Freedom is (usually) good because it (usually) reduces suffering. But it's not a given.
(Needless to say, this is not a justification for despots or kidnappers, who do not reduce but increase suffering.)
To the best of my knowledge, nothing summarises best what's “good” or “bad” or “important” than **#suffering** (avoiding it, preventing it, reducing it).
Not wellbeing, pleasure, flourishing, happiness, freedom, transcendence, detachment, or love.
And nothing seems better to me to measure and describe reality, what reality could be like, and how exactly it can be changed, than **#math** (rationality, logic, science).
Its contenders all look clearly inferior: intuition, empathy, revelation, tradition, authority, serendipity, chance, art, anecdote…
That is what “reasoning from first principles” means to me.
The causal chain may be long sometimes, with many logical steps involved. And there is room for uncertainty and for epistemic humility. But the ultimate goal is to evaluate ideas and to make decisions reducing them all to lower-level equivalents based on a few core propositions.