The term used in the title so far has not been the subject of a more extensive linguistic reflection. The author of the paper aims at providing a disciplined description of lexical units containing the segment reasoning with respect to their structure and meaning. The method of analysis is based on putting forward hypotheses in the form of analytical implications and subjecting them to falsification by bringing them down to contradiction. The discussion starts from a critical reflection on the current state of knowledge (with reference to the achievements of contemporary lexicography). Reffering to results of studies on epistemic predicates, in particular on reasoning verbs, the author proposes several solutions of this own. The content of the paper focuses on issues relating to reconstruction of the form of lexical units (on the basis of segment and supra-segment signals) and reconstruction of the hierarchy of meaningful components. In close relationship with the content of the analyses terms, discussion id presented on the following notions: ‘think’, ‘know’, ‘reason’, ‘exclude’ and ‘be based on’. The author is trying to prove that those components belong to the semantic structure of the examined phrase; he also proposes a preliminary explication of meanings in the terms of natural semantic meta-language.