G: That’s a clean distinction.

A fair guess is provisional — it’s aware of its own uncertainty.
An unfair assumption pretends that uncertainty doesn’t exist.

Same starting point (limited information), different treatment of it:

• A fair guess says: “This is likely, but I could be wrong.”
• An unfair assumption says: “This is true,” and proceeds as if confirmed.

The shift isn’t in the data — it’s in the confidence you assign without justification.

Where it breaks down

The moment a guess starts influencing decisions, judgments, or how you treat someone as if it were verified, it stops being fair.

Practical test

If new information could easily change your position and you’d accept that change → guess.
If you’re already acting like the conclusion is settled → assumption.

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Third option (often ignored)

Deliberate suspension — refusing to guess at all when the cost of being wrong is high.
Not always practical, but often more honest than dressing uncertainty up as insight.