I've been slowly acquainting myself with the later Chinese philosophical tradition. Wang Yangming (1472-1529) is one of the striking figures -- a leading neo-Confucian scholar, as well as an important provincial administrator and military commander. Perhaps his best-known thesis is the unity of knowing and acting:
There have never been people who know but do not act. Those who "know" but do not act simply do not yet know.... Seeing a beautiful color is a case of knowing, while loving a beautiful color is a case of acting. As soon as one sees that beautiful color, one naturally loves it. It is not as if you first see it and only then, intentionally, you decide to love it.... The same is true when one says that someone knows filial piety or brotherly respect. That person must already have acted with filial piety or brotherly respect before one can say she knows them. One cannot say she knows filial piety or brotherly respect simply because she knows how to say something filial or brotherly (Ivanhoe 2009 trans., p. 140-141).
Contemporary readers might tend to find this claim implausible. Aren't we all familiar with weakness of will or willful wrong action in which we do something that we know we shouldn't -- cheating on an exam, having the next drink, skipping out of a commitment to enjoy some time on the beach? Bryan Van Norden suggests that the doctrine is intended as kind of pragmatically motivated overstatement to get bookworms out of their seats, and that the strongest plausible claim in the vicinity is the claim that knowing a moral truth implies at least being motivated to act on it, even if one doesn't ultimately act accordingly. In contemporary Anglophone philosophy the view that moral judgments are necessarily motivating is called motivational internalism.
I find something attractive in Wang Yangming's doctrine, which I think doesn't quite map onto standard contemporary motivational internalist views. The doctrine resonates with my dispositional approach to belief, according to which to believe some proposition is just to act and and react as though that proposition is true. With some caveats, I might endorse the unity of believing and acting.
Here are the caveats:
1. "Action" should be interpreted very broadly. Reaction is a kind of action. Omission is a kind of action. Thinking and feeling is a kind of action. That's broader than standard use but I don't think outrageously broad. The dispositions constitutive of believing that your parents deserve your care include not only dispositions to act in outwardly caring ways but also dispositions to react inwardly with concern if they are threatened and not to forget what is important to them. If you don't generally act and react caringly, I'm inclined to say, you might sincerely judge that your parents deserve your care, and you might (in Wang Yangming's words) "know how to say something filial", but you don't fully possess the dispositional structure constitutive of believing that your parents deserve your care. (If you fail in only a few respects it might still be accurate enough to say that you believe it, similarly to its being accurate enough to call someone an extravert who is mostly disposed to extraversion but who has introverted moments.) To believe something is, on my view, to live generally as though it is so. That's the sense of "action" in question.
2. "Belief" differs from judgment and knowledge. A broad, action-based view of what is constitutive of belief only works if we also have a vocabulary for describing cases in which we sincerely verbally endorse something that we don't consistently act on. I prefer the term "judgment" for sincere endorsements. Thus, on my view, you might sincerely judge that such-and-such is the case, but if you don't generally move through the world as if it were so, you don't fully, or deeply, or completely, or univocally believe it. Similarly, I've argued (contra Wang Yangming), you can know something without believing it in this strong action-encompassing sense of "belief".
3. We often choose moral mediocrity. We can rationally choose actions we believe are morally bad. Morality is an important consideration for almost everyone, but we are often satisfied with far less than ideal moral behavior. Compare valuing health: You can believe that kale is good for your health, and thoroughly live in recognition of that fact, without always choosing kale over brownies, because health is not always your paramount concern.
You might see some tension between the third caveat and the surface interpretation of the doctrine. If the child doesn't act and react in a filial way, maybe she still does fully and unambivalently believe that her parents deserve her care, but she chooses moral mediocrity on this matter? Wouldn't that be a dissociation between believing and acting?
I do think such cases are possible, maybe even common, but that's not the kind of dissociation between believing and acting that I, and maybe Wang Yangming, want to deny. Here's one way of articulating this type of case: You don't value moral goodness much but insofar as you value it you'll care for your parents if it isn't too much trouble. That actually expresses your attitude toward filial duty; that's your belief as manifest in your actions. This differs from the case of the bookish Confucian scholar who says "I know and truly believe that filial duty is vastly more important than personal pleasures, but I just can't bring myself to act accordingly yet." Wang Yangming wants to call bullfeathers on that sort of thing. With more self-knowledge and honesty, this scholar might better say something like, "Yes, intellectually and theoretically, I judge the Confucians correct in highly prioritizing filial duty; but I don't yet personally find myself believing that filial piety is so important -- not deeply, fully, and unambivalently in the way that I deeply, fully, and unambivalently believe that this is a quill in my hand and that I must eat to stay alive."
Philosophers and others interested in the nature of attitudes can legitimately conceptualize belief in different ways. But I think there are practical advantages to accepting a broad-based notion of belief as constituted by the whole range of your choices and reactions, sharply distinguished from a more intellectual notion of judgment or sincere verbal endorsement which need not be reflected in action.
(For more on the practical advantages of a broad, action-based view of belief, see "Some Pragmatic Considerations Against Intellectualism about Belief"; April 7, 2016.)