 We have seen that advocates of a negative conception of freedom tend to count only obstacles that are external to the agent. Notice, however, that the term ‘external’ is ambiguous in this context, for it might be taken to refer either to the location of the causal source of an obstacle or to the location of the obstacle itself. Obstacles that count as ‘internal’ in terms of their own location include psychological phenomena such as ignorance, irrational desires, illusions and phobias. Such constraints can be caused in various ways: for example, they might have a genetic origin, or they might be brought about intentionally by others, as in the case of brainwashing or manipulation. In the first case we have an internal constraint brought about by natural causes, and in this sense ‘internally’; in the second, an internal constraint intentionally imposed by another human agent, and in this sense ‘externally’.