Analogy, logic, and classification

Analogical proportions are statements of the form “a is to b as c is to d”. Although analogy has essentially been thought of outside the field of logic, a representation of analogical proportions in terms of propositional logic was proposed fifteen years ago. This discussion paper mainly addresses three issues i) the problems posed by the lack of compatibility of analogical proportions with logical combination; ii) the resolution of analogical  equations between logical formulas; iii) the logical analysis of classification and the introduction of an analogical bias to allow induction.