In philosophy of mind, direction of fit is the distinguishing feature between two types of intentional mental states :

facta (singular "factum") are states with a mind-to-world direction of fit. Examples include beliefs, perceptions, hypotheses, and fantasies. In the event of a mismatch between the mental state and the world, the mental state is in some sense false or wrong and should perhaps be changed.

facienda (singular "faciendum") are states with a world-to-mind direction of fit. Examples include intentions and desires. If there is a mismatch between the mental state and the world, the world is in some sense wrong and should perhaps be changed.

In some forms of mind-body dualism, a matching factum and faciendum must be present in a person's mind in order for him to act intentionally. If a person has the belief that action A will lead to state S, and has the desire that state S obtain, then he will perform action A. The action is directly caused by simultaneous presence of the two mental states; no further explanation is needed.

The concept of direction of fit can also be applied to speech acts: declarations have word-to-world direction of fit; commands and promises have a world-to-word direction of fit.