Are we free or determined?
Behaviorists such as John Watson and B. F. Skinner believed that human behavior is determined by past events in our lives. Rather than being free, autonomous agents, we are the products of past conditioning. This raises serious questions about what extent we can hold people morally responsible for their actions.
Existentialists believe we as humans are defined by our freedom. Thus we have the responsibility to choose and follow moral principles and can be held entirely accountable for our actions and choices.