Æalogist
An æalogist (pronounced /iːˈælədʒɪst/; also spelled aealogist, ealogist, or, rarely, aialogist) is a scholar who specializes in æalogy, the study of planes and cosmoi, their comparative characteristics, and their interaction. Æalogists are very few in number compared to scholars in most other fields, because of the requirements to be able to pursue such a study. Many people aren't even aware of the existence of other planes and cosmoi as anything more than speculation and rumor, and of those who are few know anything about them more than their existence, and very few have a means of pursuing their study. Learning more about other planes and cosmoi requires either a reliable source of information on the subject, which isn't easy to come by, or a means of traveling between planes oneself, which may be even harder to obtain.
Despite all this, there are some who do manage to learn of other planes and cosmoi, and ascertain enough about them to be considered scholars on the subject. On most worlds, true æalogists are rare, with only a handful existing on an entire mound. They are substantially more common, however, in milleviae and other compits, which provide relatively easy access to other planes and thus facilitate æalogical studies.
Education
Trapped in their homeworlds, most people never have the opportunity to learn much about æalogy. Even those who have heard of other planes and want to study them may find it hard to find a reliable source of in-depth information about them. There are those who have no real knowledge of æalogy but who claim to be æalogists—or at least who claim to be expert scholars of the planes; not having come into contact with actual æalogists they may not even be familiar with the word—and whose supposed learning is all from guesswork, misunderstanding, or sheer fabrication. There are, however, legitimate æalogists, who may come by their arcane knowledge by a number of different means.
Experience
Some æalogists have had the opportunity to have direct experience with other planes, and to have traveled themselves to other planes and perhaps even other cosmoi. Often this simply comes from their living in a place with many interplanar portals, giving them an easy way to visit many different planes. Outside such areas, special powers are required to visit other planes—powers that are not easy to come by; mastering spells of interplanar travel may require years of study. These plane-traveling powers do not have to be inherent, however; some æalogists are known to avail themselves of appropriate talismans for their travels, such as magic doorknobs or betthoi. (In principle, golthoi would seem to be ideally suited to pursue æalogy, but few if any are known to have done so... then again, golthoi are extremely rare to begin with.) Some æalogists are scions of famed adventurers or other powerful individuals, motivated by stories told by their ancestors and empowered by talismans or paracarminical magics passed down from them.
There are, however, some means of learning æalogy that do not require personal experience traveling other planes. While perhaps less exciting and less thorough, these means still give the scholar an edge over those who have made no study of æalogy at all—and, of course, even those who have traveled the planes themselves may find these means useful to supplement their knowledge and find out the current state of the field.
Books
Few as æalogists are to begin with, fewer are those who have taken the time to write books on the subject. Still, some such æalogical texts do exist, such as Naka's Viae Entis; The Crystal Cotillion, by Ragi Okoro; and the anonymously written Wanderer's Guide. While also useful for those who do travel the planes, as reference works or as preparatory reading, these books have sometimes been used as a basis for a æalogical education by those with no means of traveling the planes themselves. Æalogists with actual experience with other planes are likely to look down on those who learned their subject entirely out of books, and not altogether without reason; those books on the topic that have reached wide circulation tend to be somewhat outdated and to lack information on recent developments and include old ideas since discredited, and/or to be platforms for the authors' pet theories that are at odds with the mainstream view (insofar as there are enough æalogists for there to exist a "mainstream" in the first place). Still, if not as reliable and enlightening as first-hand experience or discussion with other scholars, even these books are sufficient to give those without recourse to actual planar travel at least some cursory grounding on the subject.
Mentors
Some æalogists learned their information not from books, or not solely from books, but from predecessive mentors learned in the subject. A knowledgeable mentor can be an invaluable teacher, able to share their own learning and experience, to correct any misapprehensions the student may blunder into, and to answer questions that occur to the student's mind—even if the answer to many æalogical questions may be "nobody knows". Unfortunately, not all such mentors are as knowledgeable as they present themselves, and the "education" one gleans from a mentor who has learned his subject only from unreliable books may be worse than one acquired from reading those books directly, as the mentor layers his own miscomprehensions and speculations over those already present in his sources. In the absence of any personal experience or correction by other parties, errors accumulate with each discipular generations, until the latest in a long line of would-be æalogists taught at the feet of their precursors with no outside source of information may have learned nothing but misconceptions and misinformation and be utterly ignorant of the real state of æalogical knowledge.
Schools
Many of the potential disadvantages of learning from lone mentors are ameliorated by studying at a æalogical school. While there may be some isolated such schools where the faculty feed into each others' folly, for the most part the interaction with other æalogists keeps them from going too far astray, more so if the faculty also communicate with those of other schools. The disadvantage, of course, is that, given the rarity of æalogists, schools with good æalogical programs are very few and far between. Generally such schools exist only in milleviae where travel to other planes is easy, though there are some notable exceptions, such as the School of the Iris in the eidopolis of Maithe.
If schools that competently teach æalogy are rare, those that teach it to prepubescent students are even rarer. Nearly all æalogical schools are universities, their students adults or at least in their late adolescence. There do exist some schools where younger students learn æalogy, and where it even is considered to make up a part of the core curriculum, but they are extremely rare, and generally exist only in places where powerful magic is omnipresent and considered a basic aspect of life.
Career
Many æalogists are supported by patronage by states or powerful individuals who see value in their knowledge. Others pursue æalogy as an avocation but pursue some other employment—or rely on hoarded or inherited wealth—as their principal course of income. Those with a means of interplanar or intercosmic travel often take advantage of that for their earnings, making money by trade between different worlds.
There are, however, æalogists who make their living from their learning. A competent æalogist (or possibly even one who is incompetent but convincing) has a number of avenues they can take to earn a livelihood from it. One obvious means is teaching, but this is only an option in those rare places where æalogy is covered in education. Some æalogists work as consultants to various organizations, corporations, or individuals with æalogical interests; others simply earn money through writing or lecturing about their knowledge.
Specialists
Æalogy is a complex field with many facets, and those few scholars who do pursue it tend to find it necessary to focus on one aspect. While a competent æalogist may be knowledgeable in all aspects of the field, he will probably still have some particular specialty in which he is particularly learned. Some æalogists specialize in the study of specific planes or chorodeses, or in particular types of planes; one might be an expert on elemental planes, another on propositional planes. A perologist specializes in pocket planes; a pampherologist in cosmoi rather than planes.
Aside from specializing in specific planes, a æalogist may choose to specialize in particular aspects of planes instead, or of phenomena associated with or recurring in multiple planes. A detologist, for instance, specializes in chorodeses and in how planes interact. An antiologist specializes in alternate worlds, and in the manner of their coming into existence. A pylologist studies portals, and connections between planes; a pantothologist studies panypares; a pollachologist passivites; a palillologist ontological resonance. Not all specialties, of course, have well-established specific names; it is quite possible, for instance, for a æalogist to specialize in the study of chorogenesis, or in the comparative study of the physics of different cosmoi, but there are no terms in wide use for these specialties.
Crossdisciplinary scholars
There are savants who study not just æalogy alone, but the overlap of æalogy with other fields of learning. Comparative physicists, for instance, study the variations in the physics of different cosmoi; xenetorists study their life forms. Other comparative fields of æalogical study exist, but are represented by very small numbers of adherents.
Organizations
Despite the small numbers of æalogists, there does exist something of a æalogical community, or communities. Æalogists are, after all, aware as no others of other worlds and other cosmoi, and so it's not infeasible for them to find out about and make contact with alimundane counterparts. This isn't to say there aren't many æalogists who work in isolation, or in company with only a small group unconnected to any larger community; in fact, such lone æalogists may form a majority. But æalogical communities do exist, both in the broad sense of an informal "community" of æalogists who know each other, or at least are acquainted with each other's works, and in the more specific sense of formal organizations of æalogists.
Many of these æalogical organizations are devoted to particular specialties or other common interests. The Curio Society specializes in pantothology, the Mirror Men in antiology. The Cartularium maintains a comprehensive listing of known planes, especially pocket planes, which it publishes, in very limited circulation, in an enormous tome called the Choric Compendium. Other organizations, however, share nothing but a common origin, social ties, or the like; the whimsical Gamins' Guild originated with a like-minded group of young students in the millevia of Wickerloke and accepts new members by invitation only, while the secretive Purple Front share a goal of using their æalogical knowledge to increase their own power.
One unusually activist æalogical organization is the Ameldry, which devotes itself to sharing æalogical information with isolated worlds in preparation to their incipient contact with others. Another æalogical organization that has set itself a particular purview is the Council for Intercosmic Terminological Standardization, which strives to promulgate the use of the same terms for concepts in celemology, etory, and other complex disciplines pursued in multiple planes. While the CITS likes to take credit for this standardization, however, it's not clear how much is really due to their efforts and how much due to the same effects of ontological resonance responsible for the existence of such phenomena as panyparic languages.