`Theoretical' and `Empirical' Reasoning Modes from the Neurological Perspective

Two modes of reasoning are used by humans – the `theoretical' (formal) and the `empirical' (non-formal), the first operating with inside-the-syllogism information, the second utilising out-of-the-syllogism information. Cross-cultural research (since Lévy-Bruhl, and especially after Luria) and developmental research (since Piaget) discovered respectively that members of `traditional' societies and children up to a certain age are able to operate only in the empirical mode.The paper brings together diverse discussions about usage of these modes in actual discourse (Ennis, Johnson-Laird, Moore, Olson, Ong, etc.). It concentrates on contradictory opinions as to whether contemporary individuals after they acquire the formal mode preserve and utilise the empirical mode. In this connection it discusses results of neurological experiments investigating performance in solving syllogisms under conditions of transitory suppression of the left or the right hemisphere (Deglin et al.) which demonstrated that one and the same person, depending on which hemisphere is suppressed, uses both strategies. The activated right hemisphere utilizes the `empirical' pattern, the activated left hemisphere utilizes the `logical' pattern. Thus both mechanisms of reasoning are present in the brain simultaneously, but each of them is controlled by different hemispheres.