A scenario constructed and run entirely in the mind can produce a genuine finding about the world.

What you've already spent will be gone whatever you decide next, so it has no business entering the decision.

Do not multiply entities beyond what the explanation requires.

Working backward from failure shows what working forward toward success cannot.

Any representation of a thing is not the thing itself — and a representation is useful only to the degree that its structure matches the structure of what it represents.

How much you know matters less than knowing exactly where your knowledge runs out.

If you cannot rebuild a belief from things you can verify yourself, you don't understand it — you've only received it.

What matters most comes first; how much it gets tracks its real size, not where it ranked.

The value of a decision lives in what it sets in motion, not in what it does on contact.

How often the outcome occurs across cases like this is the first number; the particulars of any one case can adjust it, not replace it.

A belief should move when evidence arrives, and exactly as far as that evidence favours it over the alternatives.

Consistent reasoning under uncertainty takes exactly one form: probability. When we are not sure what will happen, using clear numbers for probability is the best and fairest way to show our guesses. It helps everyone understand the same thing.

Multiply each possible outcome by its probability and sum the results: that number is what the choice is worth on average — not what it will deliver this time.