Veridicality

For temporal and aspectual operators, the definition of veridicality is somewhat more complex: Negation is veridical, though of opposite polarity, sometimes called antiveridical: "Paul didn't see a snake" asserts that the statement "Paul saw a snake" is false.

The (non)veridical dependency may be positive (licensing), or negative (anti-licensing), and arises from the sensitivity semantics of polarity items.

(tag questions based on negative sentences exhibit even more such bias), can sometimes be seen as downward entailing, this approach cannot account for the general case, such as the above example where the context is perfectly neutral.

According to the formal definition of veridicality for temporal operators, future is nonveridical: that "John will buy a bottle of Merlot" is true now does not entail that "John buys a bottle of Merlot" is true at any instant up to and including now.

This is in contrast to e.g., the progressive aspect, which is veridical and prohibits negative polarity items.

Imperatives are roughly parallel to modal verbs and intensional contexts in general.