Referring to research reports and models described in the literature on the functioning of linguistic and logical knowledge in human mind, the author argues that natural, innate knowledge supporting comprehension of linguistic rules and building the structure of language is worth considering in speech therapy practice. She calls this type of knowledge logical-linguistic competence and indicates that its ability, which can be used in speech therapy practice, is to reason by analogy about the relationships of form and content between words/word forms. It is a skill that cognitive abilities and linguistic experiences develop and shape. It is, by all means, an individual feature of each person, although natural logic and lexical and grammatical features determine the areas of basic skills.