Summary.It is argued that moral values are learnt in the course of the child's development, and that consequently any theory regarding their development should be based on the known facts and principles of modern learning theory. An attempt has been made to do so by suggesting that ‘conscience’ is, in fact, a conditioned response built up during the child's formative years by the pairing of conditioned stimuli (arising from aggressive, predatory, and overtly sexual actions) and unconditioned stimuli (slaps, beatings, ‘shaming’, and other punishments) immediately following the conditioned stimulus. Aided by a process ofstimulus generalizationthis should, in course of time, lead to an association between the conditioned stimulus and the fear‐anxiety responses appropriate to the unconditioned stimulus. Certain deductions are made from this hypothesis and are shown to be supported by experimental evidence. It is argued in particular that if the hypothesis is correct, then individual differences in conditionability, i.e., the ease with which conditioned responses are formed, should be related to moral behaviour and the ease with which guilt feelings are aroused. Here also evidence is quoted to suggest that this hypothesis has some foundation in fact. It is concluded that the treatment which children, adolescents, and adults receive in response to immoral acts, should be based upon the recognition of individual differences between them, particularly with respect to their conditionability, as only in this way will the most beneficial results of such treatment be