INTRODUCTION: THE SCOPE OF MORAL PSYCHOLOGY, ANCIENT AND MODERN

Moral psychology addresses itself to the interface between ethics and psychology. One of the basic principles of moral psychology is the apparently trivial one, that all ethically correct actions are, to begin with, actions: inasmuch as they are the deliberate or at least intentional actions of human beings, ethical actions will share features with the class to which they belong, and fall under whatever constraints belong to the larger kind.

This of course raises an immediate question about the coherence of the topic so described. Psychology is clearly a descriptive field, and ethics is the normative field par excellence; the one tells us how the human mind does function, the other tells us how human agents ought to act. Given this fundamental difference, we may not assume, without further argument, that the first discussion can place any constraints whatsoever on the second. The mere fact that psychology places limits on what is humanly possible does not show, without further argument, that ethics must keep its demands within those limits.

The further argument tends to come, nowadays, in terms of a sort of mixing axiom of morality and modality, that the agent cannot be obligated to do anything it is not possible for the agent to do. This is usually abbreviated to the slogan that ‘ought’ implies ‘can’, though its teeth are more often bared in the contrapositive formulation, that ‘not possible’ implies ‘not obligatory’.