Many practitioners of various disciplines declare that their “discipline (d) does y”—that is, what it is to practice d is to do y. History is sometimes said to involve the formal seeking of knowledge regarding the psychological states of some (human) agent which have some relation of relevance to a certain event—this was the position of Collingwood. Some may say that to do history is just to attempt to gain such knowledge (whether or not success be possible or impossible)—nothing more, nothing less. Others will give other definitions on what it is to do history.
But what reason do we have for so narrowly defining what a discipline is essentially? Why must what history really is be so narrow? How are academic disciplines divided, if they can be genuinely divided at all? What does it even matter?
(I) A Fable of Philosophical Divisions
It seems to me that, if we start from the following narrative, the nature of academic disciplines should be slightly more clear: we all start doing what I will call “Philosophy.” Philosophy here is simply the seeking of a full or nearly full understanding—that is, something like a quest to know any or all truths, any or all knowable truths–it is supremely general. Included in these truths are truths about events and non-events (like mathematical objects, universals, logical principles, possible worlds, etc). To have a full understanding will be to know all truths about all events and all non-events. Since no man can possibly live up to Philosophy, we seek to narrow our focus: we seek only partial understandings. That is, we seek to know only certain truths regarding only certain events or non-events; we specialize by becoming philosophers sans Philosophy–we divide our focuses into disciplines (supposedly) according to the types of events or non-events we seek to know truths about, and we subdivide these likewise.
It seems obvious that my notion of seeking and focusing contains that of teleology, so that disciplines are not merely divided by differences in types of truths sought about kinds of subjects, but by the place that their subjects hold in inquiry. For it seems at least reasonable to suppose that it is possible for two disciplines to have complete overlap in their subject matter while still being truly distinct; further, it seems probable that one discipline may seek a set of truths about a set of subjects which contains the entirety of that which another discipline seeks, while the latter discipline should not merely be absorbed into the former as a sub-discipline. How do we explain this? Perhaps we can, as Joynt and Rescher do for history, posit that disciplines are divided by which kinds of truths and kinds of subjects are sought to be apprehended in and of themselves, or as the ultimate ends of that discipline’s inquiry.
My hypothesis, then, is that disciplines have their individuality in virtue of the types of truths about the kinds of subjects the practitioner sets as the end of his/her practices. Teleological goals, then, are the main dividers of disciplines. Those who practice history, for example, do so in virtue of purposing their various practices towards attaining knowledge of those certain types of truths regarding certain types of subjects that history has as its end (whatever they are!).
(II) First Line of Support; Differing Methodologies not Sufficient for Fundamental Divisions
Back to history as a case study: Oakesshott is said to have taken history to be a study of merely particular events; no generalizations or abstractions can feature in a truly historical explanation. Hempel and his followers disagree,  however: history must involve abstraction, for any adequate explanation of an event will be either of a D-N or I-S form. Oakesshottians and Hempelians may practice what they call “history,” although both are clearly being defined as fundamentally distinct fields.
However, both Oakeshott and Hempel, in doing history, study common subjects (or common types of subjects) (let’s say, the French Revolution, or perhaps revolutions in general). Even if we assume that their respective modes of explanation have no non-accidental overlap (which is probably false, since it seems clear to me that all explanations as to why e occurs will be of a generically Hempelian mode), we can still ask the following: is there something these two practices have in common that can justifiably lead to them being labeled as “History?” It seems prima facie probable, when we consider that they both seek to contribute portions of a full understanding of particular, human-centric events (when doing history).  If, when we investigate the particulars of their inquiry, find such a united telos, my fable of mega-Philosophy in section (I) would account well for their appearance of disciplinary unity. For my myth purports that, so long as the practices of Hempel and Oakshotte have a common telos with regards to certain types of knowledge and practices, they both belong to a common discipline (when performing these practices). What has been said here, of course, can be generalized to explaining what unites two historians despite completely non-overlapping methods (see also section (IV)).
(III) Second Line of Support; Interdisciplinary Contamination
Is it sufficient for two practitioners to belong to the same fundamental discipline if they both seek to discover truths about the same subject (or kind of subject) as the end of their practices? Ehrman will claim that historians cannot come to a conclusion regarding the occurrence of a miracle-event while still doing history—but what does this amount to? What is history? Ehrman writes that “historians by the very nature of their craft can speak only about events of the natural world.” What principle of division between history and non-history does Ehrman stand on?
One may suggest that, by incorporating (narrowly) philosophical/theological methods into historical research, one ceases to do history. But why? Philosophical methods are the backbone of every discipline—especially if what I have said about a broad conception of Philosophy is correct. Why think that interdisciplinary contaminations of this sort indicate that history has ceased and something else has begun? Consider that deduction and induction are practices underlying every discipline while knowledge of both, formally, falls under the philosophical discipline. Further, in reconstructing some historical events, psychological generalizations would be heavily relied upon.
Clearly, academic disciplines can have overlapping subjects while still retaining individuality. In fact, the account I have given for the individuality of academic disciplines seems to account well for the impossibility of academic isolation—that is, the fact that every academic discipline has deep overlap with at least one other, so that to have never practiced one discipline would probably result in the crippling of another. For, if I am correct, all academic disciplines are united as sub-divisions of Philosophy—each are joined by a supremely general concern with knowledge, and thereby a concern with truth about a perhaps infinite set of events and non-events. Supposing that any events and non-events which are understandable are so through a set of methodologies, we can see that one academic discipline may be individualized by a seeking of understanding those methodologies (which are themselves non-events). And, if this is correct, some level of disciplinary overlap between this methodological discipline and others will be inevitable. For any discipline will need to access this methodological knowledge so far as it relies on this methodological knowledge to fulfill its telos.
I will briefly clarify the argument I just offered: let us consider that there is a range of events and non-events forming the set of all events and non-events which may be referenced in true propositions. There is (at least potentially or formally) a discipline for each type of event and non-event, since there are potentially many ways one could divide that large set into subjects of seeking/inquiry. One category of non-events are methodologies. So, there is (at least in form) a discipline seeking knowledge of these methodologies. And since we would identify any knowledge about these methodologies as belonging to this discipline, we would say that any discipline which needs some bit of knowledge regarding methodologies would have content overlap with this methodological discipline. Thus, a direct consequence of my fable in (1) is exactly what we find in our own experience, for every academic discipline does rely on such a methodological discipline (which some have identified as philosophy in particular).
(IV) Anticipating Objections; Defeating an Entrenched Principle; Third Line of Support
Perhaps one may suggest that any attempt of doing history and coming to a miracle-event-conclusion will fail to apprehend the relevant truths, and thereby say that, because any attempt of doing history this way is inadequate, it cannot truly be considered history. That is, some seem to reason that, because doing x fails to or cannot possibly accomplish what some discipline seeks to do, that doing x cannot be an action considered within that discipline. In my reading, AJ Ayer divided speculative metaphysics from philosophy on this principle, as well as Oakeshott; it also seems likely that Hempel would declare any historical explanation which does not even tacitly involve a D-N or I-S explanation as inadequate (since we can only attain the relevant knowledge by explaining in such a way), and therefore inadequately historical.
Consider, though, the following situation: Bridget, a history student working on her doctoral dissertation, is seeking to provide an explanation for why Alexander Hamilton threw away his shot, and subsequently opened himself up to death. Let’s suppose that this scholar has consciously decided to seek the truth about a small event in history: that is, she, through her work, is attempting to discover the causal process which led to Hamilton’s firing in the air. However, she fails to come up with a correct explanation—in fact, her methodology with which she explains events could never correctly explain any event, for it intimately involves an acceptance of backwards causation (and I assume this is an incoherent notion). Should we say that her account is non-historical? If we make use of the principle previously laid out, we would have to, for she both fails to attain knowledge about a historical event and could not possibly do so through her explanation. But it seems obvious to me that she is practicing history, though she is practicing bad history.
Our judgement that Bridget is doing history despite not possibly being able to fulfill the function of the historian is consonant with the account laid down in (I). Further, my hypothesis is made more plausible given that it provides an answer to, “why is Bridget doing history despite such failure?” For Bridget’s intentions regarding her practices are to fulfill such a function (whatever it is), and according to my account this alone is sufficient for doing history.
I conclude, on the basis of the intuitive plausibility of my hypothesis and its explanatory power evidenced in sections (II-IV), that disciplines have their individuality in virtue of the types of truths about the kinds of subjects the practitioner sets as the end of his/her practices. Teleological goals, then, are probably the main dividers of academic disciplines.
 Dray, William. Philosophy of History. 10-12. It may be suggested that Collingwood simply believed that
 The etymology of “philosophy” seems to bear out this broad conception of philosophy.
 Rescher and Joynt. “The Problem of Uniqueness in History.” 153.
 I am writing here of only academic disciplines, which clearly have sorts of knowledge as their ends (academic disciplines are all fundamentally Philosophical subdivisions); but a similar principle of division for the non-academic disciplines is not far from us. We can perhaps say that non-knowledge-seeking disciplines are divided according to their goals; the athlete has as their end some sort of physical proficiency, and the auto-mechanic something like the preservation of proper automotive functioning. It is worthy to note that here seems to lie the most fundamental division of human disciplines: the division between Philosophical and non-Philosophical—knowledge seeking and non-knowledge seeking.
 Dray, 8.
 (Dray. p8) Hempel would probably say that Oakeshott was practicing history, even despite his lack of D-N or I-S explanations, so long as he (whether he knew it or not) was tacitly giving them in giving a historical explanation. Oakeshott would not, however, be so charitable: any generalization was anathema to the historian.
 (Dray, 9.) Roughly, D-N explanations posit a general law and particular circumstance which, when combined, imply that the event in question will occur. I-S explanations posit a general law and particular circumstance which, when combined, implies that the event in question is more-likely-than-not to occur. Both explanation forms answer the question “why” e has occurred by attempting to reconstruct the actual sufficient conditions for e or the plausibility of e. Many detailed theories of D-N and I-S explanations exist, but teasing out a particular account is not currently important.
 I am, of course, aware that neither Oakeshott nor Hempel were properly considered historians, but this matters not. Take my reference to their doing history as reference to those who follow their methodologies’ practices.
 I do not mean this to be taken as the necessary and sufficient conditions for the discipline of History.
 The issue of the essence of what it is they do is complex—and their practices may have distinct essences while still being united by one, perhaps just as Pierce and Emily are both essentially man, yet Emily is not essentially Pierce, while Pierce is, and vice versa. These two instances of man share a common nature, while also having a distinct nature (I am here using nature and essence interchangeably).
 Ehrman, Bart. “Historians and the Problem of Miracle.” (https://ehrmanblog.org/historians-problem-miracle-members)
 For then every discipline would be a sub-discipline of philosophy.
 (Ayer, AJ. “Language, Truth and Logic.” 1952. Ch1.) Consider just why Ayer cuts so much from philosophy: the pseudo-philosophical could never attain to truth, given the unverifiability and thus meaninglessness of their questions and hypotheses.
 Rosenberg, Alex. Introduction to the Philosophy of Science. 2011. Ch3.