The Evolution of Turing's constructivism: from the logic of thought to the morphogenesis of idea

The two main aspects involved in the notion of construction, i.e. the structural and the genetic, are scrutinized through Turing’s intellectual evolution. These two aspects are defined by Turing thanks to two notions which co-evolve: that of form on the one hand and that of mental act on the other. During the first structural – logico-combinatorial in nature – period of his career, the notion of form is interpreted by Turing in a formal sense and the notion of mental act is defined as a finitist behaviour that can be modelled by rules of re-writing. In a second stage, linked to the discovery of organization in complex living phenomena, the notion of form is interpreted as a stabilisation phase in emerging processes and the notion of mental act as the production of forms. In describing the conditions by which forms can stabilize, Turing was trying to describe at the same time the conditions by which a mental act can be produced: from this point of view, conceptual and personal aspects intermingled.