Inference versus assumption in light of the Finnish evidential-modal adverbs näköjään and varmaan

Inference is usually defined as a speaker’s personal but indirect evidence that is based on something that the speaker can directly witness (such as the result of an event), while assumption is based on something such as the speaker’s general knowledge of the world. This paper is concerned with inference and assumption in light of the semantics of the Finnish inferential and assumptive adverbs näköjään (inference) and varmaan (assumption). These are examined by administering a questionnaire study. The discussed scenarios differ according to three factors: the presence or lack of visual or sensory evidence, the temporal relations between the evidence and the claim that is made, and the strength of the evidence. The results of the study clearly establish that inference and assumption are separate notions (coded by different adverbs) and that the (non-) observability of the evidence noted above explains only a part of the attested cases; in general, the use of the adverbs is determined by how reliable the speaker considers the evidence to be. As a consequence, this paper proposes new definitions based on the speakers’ selection of the appropriate inferential/assumptive adverb based on how strongly they are willing to vouch for the truth value of their statement.