A duty is owed, an obligation is binding; for if something is owed, then there is a debt; and if there is a debt, there is a creditor (moral or otherwise). An obligation is binding: etymologically, ob + ligere = concerning + (to tie). If there is a creditor, then there is an exchange between two parties; if there is an obligation, then there is action by only one of them. So the Roman Republic knew duty, just as did the feudal order in Europe; the very assertion of a duty implies reciprocity of some kind. This sense has perhaps been lost in the 20th century.
“Duty” is an Anglo-Saxon word: “that which is owed.” The French don’t have it but they use devoir. Fealty and loyalty are two different types of duty; neither qualifies as an obligation. Fealty is from a vassal to his lord; loyalty is from a knight to his prince. Loyalty is from a military general to a republic; obligation is from a military general to a tyrant. (By tyrant I mean a tyrant in the modern sense, more like Peisistratos Jr. than Peisistratos Sr.). The French devoir combines the two senses, which are separable by context. Devoir can be an absolute moral duty to an uncompromising authority, and it can also mean homework assigned by a teacher: which in French schools amounts to the same thing.
Duty is felt, obligations may be imposed; or responsibility is a modern form of duty, in some senses. Duties are assumed by the individual; obligations are imposed by the superior. Duty is “ought”; obligation is “must”. Today one’s obligations can overwhelm too easily one’s duties. To assume duties requires an experiential moral space that incessant obligations too easily annihilate. Especially when those obligations are internalized in a master/slave relation to the superior authority, one loses autonomy; and some relative autonomy seems necessary for duties to be recognized and so assumed.
Autonomy is the foundation of duty, subordination is the foundation of obligation. Autonomy is difficult to found (not find) within a totalizing (not totalitarian) reality. Autonomy can be grounded only in reference to concrete “really existing” historical and social circumstances. Then autonomy can become an Archimedean point (fulcrum) between what precedes and what follows. In the postmodern world, duty can arise only out of immanent critique, because the postmodern world is, exactly, totalizing: immanent critique grounded in aforementioned autonomy.
Obsession is a fixation on obligation, compulsion is a fixation on duty; and both are towards oneself. Under obsession, the obligation is introjected; under compulsion, the duty is internalized. Obsession and compulsion in moderation are not to be sneezed at. Duty may give rise to obligation, but obligation can annihilate duty. Passion is the striving after an object from which one feels apart. Passion is a more or less naked drive. To be more precise, passion is not a drive, but passion is driven by a quest for wholeness. Passion is driven by the quest for a state of being or mind. Obsession and compulsion are detours/dead-ends/roundabouts on the road of that quest. They are forms that such a “drive” may but need not take.
Love has at least two kinds, Amor and Agape. Amor is physical love, Agape is spiritual love (in 10 words or less). Agape is not far from what is sometimes called altruism but is perhaps more accurately called lovingkindness. Passion can be a phenomenon of each kind of love. Passion is not possible without love?! Passion may be the seeking after love if it is love from which one feels apart! Passion “manifests” as obsession and compulsion together, but not all obsessive-compulsives act passionately or seek after love.
Passion requires autonomy seeking after wholeness. Autonomy is the foundation of duty. Passion is impossible in the absence of duty, unless Autonomy does not require duty. If passion requires autonomy seeking after wholeness, and autonomy is the foundation of duty, then passion requires the foundation of duty seeking after wholeness, which wholeness is, for duty, accomplishment: as duty means that which is due or owed, and accomplishment means to be filled up (with achievement and/or qualities depending upon context). Accomplishment carries the sense of duty fulfilled, the duty successfully to have sought after that from which one was apart.
Duty implies respect for the one to whom duty is owed; obligation does not. That is why self-obligation can be exhausting. What is a word for “self-duty”? “Duty” in Greek could mean “what is fitting” or “what is necessary”. We have been using “obligation” to refer to the latter. Greek “what is fitting” is to prepon and to prosekon; “what is necessary” is ta deonta. To prosekon appears to mean “to come to (a place)”; so a duty is something that meets or is met. It is established that passion, driven by the quest for a state of being or mind, is the striving after an object from which one feels apart.
Duty – to prosekon (that which is fitting) – is something that meets and is met; and that which meets and is met, is that after which there is striving: as well as the dutiful one, who also meets and is met by that after which there has been striving. Now obligation – to deonta (the deontological) – refers to that which is binding, hence obligatory (ob + ligere).
The phrase “rights and duties” often occurs in common parlance. “Rights” are in fact obligations to others, seen from their point of view; duties are assumed autonomously on your account. To have an obligation to myself or another, implies that myself or another has the right to expect and receive the fruit of the execution of that obligation.
There is no word for “self-duty” that I can find in the manner of the word “self-obligation” (“duty to oneself” is a different construction). I hazard that that is because “duty” carries the sense of “self” within, such that “self-duty” is a tautology. If “self-obligation” literally means tying oneself to oneself, then it is something for masochists.
The “core” of obligation is external, the “core” of duty is internal. One has obligations to pay and duties to fulfill. Of course you pay customs duties but that is an older usage that has somehow survived; because you are obliged to pay them. The etymological link between fulfillment and accomplishment is present in the sense of duty: “fulfillment” is just Anglo-Saxon for the Latin “accomplishment”. The accomplishment of a duty is fulfilling, the execution of an obligation is merely liberating. [Ful- = accom- and -fill = -plish (pleo, plere).]
Duty creates space, obligation reduces it. Passion can never ever be an obligation, but love can create duty; and autonomy is a precondition of duty. It does not automatically follow that love can create autonomy, but in fact it can do so, on the way to duty. So we have the apparent paradox that love can create autonomy; this paradox is resolved in that autonomy does not exist without an Other.
From duty also obligation may arise. This does not mean that obligation does not reciprocally create (other) duties. Love creates the duty to care for the other’s well-being and the duty to care for oneself for the sake of the other.