Alethic modality (from Greek

ἀλήθεια ''Aletheia'' or Alethia (; grc, ἀλήθεια) is truth or disclosure in philosophy. Originating in Ancient Greek philosophy, the term was later used in the works of 20th-century philosopher Martin Heidegger. Although often translated as "tr ...

= truth) is a

linguistic modality In linguistics and philosophy, modality refers to the ways language can express various relationships to reality or truth. For instance, a modal expression may convey that something is likely, desirable, or permissible. Quintessential modal ex ...

that indicates modalities of truth, in particular the modalities of logical necessity, contingency, possibility and impossibility. Alethic modality is often associated with

epistemic modality Epistemic modality is a sub-type of linguistic modality that encompasses knowledge, belief, or credence in a proposition. Epistemic modality is exemplified by the English modals ''may'', ''might'', ''must''. However, it occurs cross-linguistical ...

in research, and it has been questioned whether this modality should be considered distinct from epistemic modality which denotes the speaker's evaluation or judgment of the truth. The criticism states that there is no real difference between "the truth in the world" (alethic) and "the truth in an individual's mind" (epistemic). An investigation has not found a single language in which alethic and epistemic modalities would be formally distinguished, for example by the means of a

grammatical mood In linguistics, grammatical mood is a grammatical feature of verbs, used for signaling modality. That is, it is the use of verbal inflections that allow speakers to express their attitude toward what they are saying (for example, a statement of ...

. In such a language, "A circle can't be square", "can't be" would be expressed by an alethic mood, whereas for "He can't be that wealthy", "can't be" would be expressed by an epistemic mood. As we can see, this is not a distinction drawn in English grammar. "You can't give these plants too much water." is a well-known play on the distinction between perhaps alethic and hortatory or injunctive modalities (it can mean either "it is impossible to give these plants too much water = giving them too much water is harmless" or "you must not give these plants too much water = giving them too much water is harmful"). The dilemma is fairly easily resolved when listening through paralinguistic cues and particularly suprasegmental cues (intonation). So while there may not be a morphologically based alethic mood, this does not seem to preclude the usefulness of distinguishing between these two types of modes. Alethic modality might then concern what are considered to be apodictic statements.

References

Grammatical moods Modal logic Linguistic modality Semantics {{grammar-stub