意向性(intentionality)
导向一个客体的属性。意向性以各式不同心理现象呈现。譬如，一个人若对一个客体有情绪感觉，他就是对该客体有意向态度。其他对客体有意向态度之例是：寻找（looking for）、相信（believing in）与思及念及（thinking about）。意向态度也包括命题态度（propositional attitude）。意向性的一项特徵是「不存在」（inexistence）：一个人可能在意向上关联到一个不存在的客体。因此，一个人所寻找（且有意寻找）的对象可能并不存在，而且他或她所相信发生的事情可能完全不存在。另一项特徵是指涉不明（referential opacity）：一个将意向状态如实归属於某人的句子，当关於该意向客体的描述被另一描述所取代时，那个句子就变成错的。假设我的笔是今年制造的第一百万枝笔，所以「我的笔」跟「今年制造的第一百万枝笔」有相同的指涉。我有可能是处於寻找我的笔的意向状态下，而非处於寻找今年制造的第一百万枝笔的意向状态下；同样的，我有可能相信这是我的笔，但不相信这是今年制造的第一百万枝笔。
English version：
intentionality
Property of being directed toward an object. Intentionality is exhibited in various mental phenomena. Thus, if a person experiences an emotion toward an object, he has an intentional attitude toward it. Other examples of intentional attitudes toward an object are, looking for, believing in, and thinking about. Intentional attitudes also include propositional attitudes. One characteristic of intentionality is “inexistence”: A person may be intentionally related to an object that does not exist. Thus, what a person looks for (and intentionally seeks) may not exist, and an event he or she believes to occur may not occur at all. Another characteristic is referential opacity: A sentence truly ascribing an intentional state to a person will become false when some alternative description of the object of that state is substituted for it. Suppose that my pen is the millionth pen produced this year, so that “my pen” and “the millionth pen produced this year” have the same reference. I may be in the intentional state of searching for it as my pen but not in a state of searching for the millionth pen produced this year; similarly, I may believe that this is my pen and yet not believe this is the millionth pen produced this year.