A semantic condition that describes the precise circumstances under which a formula $\phi$ may be asserted. The assertability conditions for a formula $\phi$ are similar to the truth conditions for $\phi$, i.e., the account of circumstances in which $\phi$ is true, but may diverge in some cases. The distinctions emerge because the definitions of particular assertability conditions in proof-theoretic semantics rely heavily on the interpretation of intuitionistic logic, e.g., they closely resemble the clauses in the Brouwer-Heyting-Kolmogorov interpretation of intuitionistic logic. Hence, while the classical truth condition for negation may be described as:

• • $\neg \phi$ is true if $\phi$ is not true

the assertability condition commonly associated with intuitionist negation appears as:

• • $\neg \phi$ is assertable if one has a method of showing that $\phi$ entails an absurdity.