An intention is a mental state in which a person commits themselves to a course of action. Having the plan to visit the zoo tomorrow is an example of an intention. The action plan is the content of the intention while the commitment is the attitude towards this content. Other mental states can have action plans as their content, as when one admires a plan, but differ from intentions since they do not involve a practical commitment to realizing this plan. Successful intentions bring about the intended course of action while unsuccessful intentions fail to do so. Intentions, like many other mental states, have intentionality: they represent possible states of affairs.
Theories of intention try to capture the characteristic features of intentions. The belief-desire theory is the traditionally dominant approach. According to a simple version of it, having an intention is nothing but having a desire to perform a certain action and a belief that one will perform this action. Belief-desire theories are frequently criticized based on the fact that neither beliefs nor desires involve a practical commitment to performing an action, which is often illustrated in various counterexamples. The evaluation theory tries to overcome this problem by explaining intentions in terms of unconditional evaluations. That is to say that intentions do not just present the intended course of action as good in some respect, as is the case for desires, but as good all things considered. This approach has problems in explaining cases of akrasia, i.e. that agents do not always intend what they see as the best course of action. A closely related theory identifies intentions not with unconditional evaluations but with predominant desires. It states that intending to do something consists in desiring it the most. Opponents of this approach have articulated various counterexamples with the goal of showing that intentions do not always coincide with the agent's strongest desire. A different approach to the theories mentioned so far is due to Elizabeth Anscombe and denies the distinction between intentions and actions. On her view, to intend a goal is already a form of acting towards this goal and therefore not a distinct mental state. This account struggles to explain cases in which intentions and actions seem to come apart, as when the agent is not currently doing anything towards realizing their plan or in the case of failed actions. The self-referentiality theory suggests that intentions are self-referential, i.e. that they do not just represent the intended course of action but also represent themselves as the cause of the action. But the claim that this happens on the level of the content of the intention has been contested.
The term "intention" refers to a group of related phenomena. For this reason, theorists often distinguish various types of intentions in order to avoid misunderstandings. The most-discussed distinction is that between prospective and immediate intentions. Prospective intentions, also known as "prior intentions", involve plans for the future. They can be subdivided according to how far they plan ahead: proximal intentions involve plans for what one wants to do straightaway whereas distal intentions are concerned with a more remote future. Immediate intentions, on the other hand, are intentions that guide the agent while they are performing the action in question. They are also called "intentions-in-action" or "act-related" intentions. The term "intention" usually refers to anticipated means or ends that motivate the agent. But in some cases, it can refer to anticipated side-effects that are neither means nor ends to the agent. In this case, the term "oblique intention" is sometimes used. Intentions are rationally evaluable: they are either rational or irrational. Conscious intentions are the paradigmatic form of intention: in them, the agent is aware of their goals. But it has been suggested that actions can also be guided by unconscious intentions of which the agent is not aware.
The formation of intentions is sometimes preceded by the deliberation of promising alternative courses of action and may happen in decisions, in which the agent chooses between these alternatives. Intentions are responsible for initiating, sustaining, and terminating actions and are frequently used to explain why people engage in a certain behavior. Understanding the behavior of others in terms of intentions already happens in early childhood. Important in this context is the role of gestures, pointing, attention, and eye movement to understand the intentions of others and to form shared intentions. In the philosophy of action, a central question is whether it is true for all intentional actions that they are caused or accompanied by intentions. The theory of reasoned action aims to predict behavior based on how pre-existing attitudes and subjective norms determine behavioral intentions. In ethics, the intention principle states that whether an action is morally permissible sometimes depends on the agent's intention for performing this action.