When philosophers write about action, what they mostly have in mind is events in which something mental becomes realised by the body through the agent's will. The work of the will is to translate the mental antecedent, which may be a desire, or an intention, or more generally some kind of pro-attitude, to the bodily realm. The mental antecedent of action gives the aim, the agent has beliefs as to how to reach it, and the will (or acts of will) has the role of executor. There are versions of causal theories of action where the role of the will is redundant. What happens in an action is just that the pro-attitudes cause the relevant bodily movements in the right way. In any case, it seems that this view of what could be called overt actions is rather natural. In overt actions, the body is governed by the mind. However, there are also actions that could be labelled as acts of the understanding or doxastic actions. Forming a belief on the basis of evidence seems to require an act of the understanding. Inferring from premises to a conclusion seems to be an active process - not something that just happens to the person. For these kinds of actions it is difficult, or perhaps impossible, to give a purely causal account in terms of beliefs causing other beliefs. It is the agent who draws the conclusion and has to take care of the inference going right or of the belief being formed correctly by the evidence at hand. What is distinctive to these kinds of actions is that there is a sense in which the agent involved in them does not aim at good, or does not try to get rid of some uneasiness, but aims at truth. These kinds of acts may be called acts of the understanding.