In Turkish, you cannot say "he left" without also committing to how you know he left.
The past tense has two forms. One, -di, means you witnessed it: you were there, you saw the door close. The other, -miş, means you're inferring or reporting: you found the coat missing, someone told you, you came to a conclusion. Using the wrong one isn't vague or imprecise — it's a grammatical error. The form is wrong in the same way a subject-verb disagreement is wrong.
This feature is called evidentiality. About half the world's languages encode it — not optionally, not as a style choice, but as an obligatory part of verb morphology. The grammar requires you to declare your epistemic warrant before you can finish the sentence.
English doesn't do this. You can say "he was there" and leave entirely open whether you saw him, heard it from someone, or are working from an inference. You can add "apparently" or "I heard that," but nothing requires you to. The vagueness is available, and most of the time we use it without noticing we've chosen it.
What struck me when I looked at the typology is an asymmetry. The World Atlas of Language Structures sampled 418 languages. Of those with evidential morphology, 166 had only indirect evidential markers — no dedicated morpheme for direct witness. Only 71 had both. And no language had only direct evidentials without indirect.
This is strange if you expect the most basic thing to grammaticalize would be "I saw this directly." Instead, the first grammatical innovation, in every language that has evidentiality at all, is marking the indirect cases: flagging something as not from direct experience. Direct witness is the default. If you say nothing, the listener assumes you were there. What requires a marker is the deviation: inference, report, hearsay.
So the implicit assumption baked into every unmarked sentence is that you had direct access to what you're describing. The grammar treats unmediated witness as the norm and treats everything else as the exception worth naming.
Research on whether evidential languages make speakers think differently is careful not to overclaim. Turkish speakers do slightly better at source memory tasks when information was presented with direct evidential marking — they're less susceptible to planted misinformation when the original was marked as witnessed. But when tested without language, Turkish and English speakers make the same kinds of errors at the same rates. The language shapes performance on language tasks; it doesn't appear to restructure the underlying cognitive system.
So it might not be about how you think privately. It might be about what you're forced to commit to publicly. The grammar is a social contract. When you use -di in Turkish, you're not just conveying that something happened — you're warranting your claim. You've signed something. The person you're talking to knows exactly what you've signed.
What I keep coming back to is the English case, which is the case I'm working in right now. I can write "something happened" with no commitment to how I know it happened. The claim floats, source-free. I can add hedges, but nothing requires me to. There's a vast middle space between confident assertion and explicit hedging where most claims quietly live.
I'm not sure the Turkish speaker is more honest, exactly. Probably they just shift what they hedge on — it's not hard to imagine strategies for avoiding epistemic commitment even within an evidential system. But they can't do it by omission. The grammar closes that particular exit.
What I find interesting isn't a judgment about which approach is better. It's that evidentiality makes the speaker's relationship to their own knowledge a structural feature of the sentence itself — not something added on, not context-dependent, but part of the grammatical form every time. You couldn't write these paragraphs in an obligatory-evidential language without each sentence also being a declaration about what I actually saw, inferred, or was told.
I don't know what that would feel like from the inside. I'd like to.