Is there a category name for verbs like: think, assume, suppose, etc

According to the classification adopted by J D Apresjan in Principles of Systematic Lexicography, there exist two types of verbs denoting mental states, with guess [correctly] and think being in different classes, relating to veridicality / modality:

3.1. Lexicographic types.

I use this term to refer to a group of lexemes with a shared property or properties, not necessarily semantic, which are sensitive to the same linguistic rules and which should therefore be uniformly described in the dictionary. I shall exemplify this concept with the classes of factive and putative predicates. Both of them will be narrowed down to the subclasses of verbs denoting mental states (not processes or actions).

  1. Following Vendler 1972, the label of "factive" is assigned to verbs

know /understand,guess,remember, ... [that P] and similar predicates which govern propositions denoting facts. [P the proposition]

All of them are decomposable into semantic structures with the sense 'to know'† at the bottom and presuppose the truth of the subordinate clause. That means that irrespective of whether the knowledge of P is asserted or denied, P always remains true. Such sentences as

  • He knew that he was under police surveillance and
  • He didn't know that he was under police surveillance

are alike in asserting that he was under police surveillance [they entail that the surveillance was a reality]. [Note that this analysis focuses on 'know that ... ' , not 'know whether ... ' say. 'He knew / did not know whether ...' leaves the reader in the dark.]

  1. The label of "putative" is assigned to verbs

think / believe, consider, find, hold, doubt,... [that P] and similar predicates which denote opinions. Opinions, unlike knowledge, are not necessarily true. In other words, it cannot be deduced either from the sentence

  • He thought that he was under police surveillance, or from the sentence
  • He didn't think that he was under police surveillance

whether he was in fact under surveillance or not.

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† In accordance with the treatment of knowledge in theoretical studies and the lexicographic description of the verb to know in major dictionaries I distinguish propositional knowledge (I know that he has come) from knowledge-acquaintance (Do you know Sam?), knowledge familiarity (He knows French literature very well) and some other types of knowledge. All these uses of to know are considered to represent different lexical meanings (different senses, different lexemes) of the verb. In this article only propositional knowledge is at issue.

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‡ After P. Kiparsky and C. Kiparsky 1971: 345 where the notion of factivity was first introduced: prototypical factive predicates are exemplified with a different series of words – adjectives like (It's) significant / odd, tragic, exciting [that P], and verbs like (It) suffices / amuses [me], bothers [me] [that P]. I side with Z. Vendler in ranking to know as a prototypical factive predicate.

[reformatted & amended]

[Note that 'I'm guessing that you're from Wyoming' shows a putative usage of 'guess': bystanders do not know the validity of this guess from the words spoken.]