Yes, pietas is better, but I don't think that the Romans had a word for "duty" in a particular modern sense: doing what one requires of oneself based solely upon ones own concept of duty, rather than upon personal devotion or official obligation. I don't think that either officium or pietas could properly be used to translate Oscar Wilde's statement that: "Mr. Henry James writes fiction as if it were a painful duty."Duty: certainly officium is technically correct in this sense, but seems a bit impersonal. I would suggest pietas, which expresses a duty to the gods, family (particularly parents), friends, and country; duty based on personal devotion.
I agree, as well: Consentio cum Bitmap et Pacifica. Inspicite quaeso, ut alia praetermittam, Thesaurum Linguae Latinae (TLL) s. v. officium. Permulta ibi exempla afferuntur quibus officium confirmatur. Cic. inv. 1, 6:In that sentence, officium would actually work well, I think.
Mar. Victorin. rhet. p. 197, 14:id quod facere debet (sc. orator), officium esse dicimus
Coniungunter saepe cum hac notione officii denominationes professionum: officium vilici, tonsoris, remigis, rhetoris, oratoris, medici, militis (cf. Caes. Gall. 5, 33, 2: Cotta ... in pugna militis officia praestabat) &c..officium, quod ex legibus vel ex natura necesse est nos implere
... Oscar Wilde's statement that: "Mr. Henry James writes fiction as if it were a painful duty."
Source of quotation:Where did he say that? ...