Elbers* does an excellent job of integrating, analyzing, and extending recent theoretical and empirical work concerning the relation of learning and development. The purpose of this commentary is to challenge Elbers to address the difficult question of universal sequences in human development. In order to focus the issue, a specific sequence in the development of logical reasoning is proposed.

We want to show the difference between the degrees of possibilities (or necessities) and the degrees of belief (or plausibility). The overall principle is that the degrees of possibilities and necessities are the extensions of the modal concept of possibility and necessity whereas degrees of belief and plausibility are related to a language at a metalevel. Two models are considered: the transfe...