Life is a quality that distinguishes objects which have some manner of (not necessarily conscious) self-drive and self-preservational processes from inert objects that are passively subject to their environments. An object possessing life is said to be alive, and is called a life form, or a living thing; the verb "to live" means to possess life. (The word "life" can also be used to refer to living things collectively.) This definition is by nature somewhat vague and subjective, and it's not always clear what objects are alive and which are not. Certainly humans and other animals are alive, and almost anyone would agree that rocks and drops of water are not, but for some objects the matter is less clear cut: viruses have some properties of life, but not enough for there to be a universal consensus that they count as living things; one could also argue whether, for instance, mitochondria are possessed of a life of their own. On a larger scale, there are those who count cities and other complex, organized collections of intelligent (or not) life forms to also be distinct life forms in their own right.
An object which is not alive is said to be "anetoric", or "inanimate". While the latter is more common (particularly in nontechnical contexts), the two words have slightly different connotations: "inanimate" may also be applied to objects that are living but immobile, while "anetoric" unambiguously describes an object as nonliving. Thus sponges and trees, for instance, may be inanimate but not anetoric. The adjective "abiotic" is sometimes confused with "anetoric", but refers more properly to things that are not associated with the universe Biota (comprising organisms). Seins, undead, and talans, for instance, are all (at least arguably) living, but abiotic. The magical process of bestowing life on a formerly inanimate object is known as animation.
The adjective "vital" refers to life. The study of life and of living things is called etory (not to be confused with biology, which is the study of organisms, a particular subgroup of living things).
Often life is defined according to a set of particular criteria. Living organisms take in nutrients, reproduce, and react to their environments. While such an itemized definition seems alluring, it is highly problematic. Reacting to the environment is particularly broad; any object reacts to its environment to some degree, even if only to move when pushed, and while it may seem clear that these simple reactions are qualitatively different from those really diagnostic of life, it's nontrivial to rigorously define just what that difference is—especially considering that the complex reactions and behavior of living things at their foundation stem from a complicated collection of such simple processes. The other standard criteria are also met by objects that are not normally considered alive. Rivers take in water that could be considered their nutrients. Simple computer viruses can reproduce. Crystals, introduced into supersaturated solutions, do both: they cause the growth of more crystals, drawing on the chemicals in the solution. Yet only the most fanatically inclusive would propose that these crystals are alive. Moreover, there are things that don't meet these criteria that are universally considered alive. Worker bees don't reproduce; neither, for that matter, do many humans (eunuchs, those too old or too young, or the otherwise infertile)—yet they're certainly alive. One could broaden the definition to include them on the grounds that they are clearly related to and conspecific with other entities that can reproduce—but then it's not easy to give a good reason why that same argument can't apply to, say, a corpse.
It's possible to define things a little more carefully and exclude such shallow exceptions. But it may not be possible to ever reach a definition—or an intuitive understanding—that makes it possible to unambiguously categorize everything as either alive or anetoric. It may, perhaps, be most workable—and most rational—to not regard life as a binary property. The simplicity of a property being either wholly absent or wholly present may appeal to the human mind, but may not really reflect reality. Rather than any given thing being either definitely alive or definitely not, there is a continuum in which some objects—such as viruses—lie between the two extremes of "living" and "nonliving".
Living beings come in enormous diversity, and may have various different origins. Some living things simply arise naturally out of chemical processes, starting with simple self-replicating molecules or other units and their descendents over time growing in complexity and diversifying through the process of biological evolution. Others are created by other living things, either intentionally or as a byproduct of some other process. Still others may be brought into existence by magical means. Once life arises, by whatever means, many kinds of life form have the ability to reproduce and replenish their own numbers. In the case of complex biotic organisms, this may occur through an involved process of sexual reproduction by which the parents intermingle the genes that direct their form and development, although many organisms can reproduce simply by dividing in two, or by yet other means. Abiotic life forms may reproduce magically, or by constructing new exemplars out of materials from the environment, or in some cases (such as that of many undead) even by converting other life forms into others like them.
Whatever the case, most living things are exemplars of pluressent types, either through common descent or because they came to exist by similar methods. These types can in turn be associated with others that are similar, and so on up various levels. This is the basis of etorical taxonomy, a system used by etorists to categorize all living things and to try to clarify their relationships. At the basic level, all living things that are sufficiently similar to reproduce with each other or by near-identical methods are considered to belong to the same species, the finest major taxonomic classification. Related species are then collected into genera, and so on, up to the broadest level, the universe, comprising all living things that are brought into being by the same basic kinds of processes.
As life is necessarily something of a vaguely defined quality, there are many different views on what exactly qualifies as a living thing. While biotic organisms are more or less universally considered to be living (especially by other biotic organisms), the other universes are more controvertible, or at least more controverted. Even aside from these fairly conventional differences of opinion, there are some philosophies outside the mainstream that nevertheless have significant numbers of followers and are more or less coherent. None of these philosophies is prevalent on True Earth, but they may have significant sway on some other worlds.
The doctrine of hathroics defines life by its property of self-organization, and follows this to its conclusion that any self-organized system is alive, including systems of other living beings. That is, an ant hive or a prairie dog colony is itself a living thing, composed of but not identical to the individual ants or prairie dogs that make it up—and the same is true of human communities. Such an entity made up of other living things is called a hathron. Hathra may run many layers deep; a sovereign state may be a hathra composed of its several administrative divisions, which in turn are composed of cities, which in turn are composed of neighborhoods. Hathra also can, and commonly do, overlap; the same individual may, for instance, work for a company, attend a church, hold membership in a club, and be a citizen of a nation each of which is a separate hathron. Some hathroists (proponents of hathroics) believe that, just as a human is far more aware and intelligent than their individual cells, so too a hathron may be at a level of being far above its components; a large nation is a being vastly exceeding humans in intellect and understanding. (One might, and occasionally does, question why therefore nations often act so stupidly.)
Tyctothymy is the idea that manufactured objects are in a sense alive—not just patently self-directed ones like seins and talans, but other machines and mechanisms as well. Tyctothymists argue that while manufactured objects do not directly reproduce themselves, they do play an indirect role in their own reproduction in that if an object serves its purpose well, its makers will tend to manufacture more objects similar to it. This principle can be extrapolated to the conclusion that manufactured objects experience a process of evolution similar to the biological evolution undergone by biotic organisms. Other properties of life, too, are shared by many if not all manufactured objects: the taking in of nutrients (fuel), the reacting to environments, and so forth. Different schools of thought draw the line in different places; some tyctothymists hold that all manufactured objects are alive, while others reserve the distinction only for those passing some threshold of complexity, or those that run on some power source. To most tyctothymists, the fact that an object is alive does not necessarily imply it is sentient; objects may be alive but insensate, much like (presumably) simple fungi and microorganisms. However, some tyctothymists do, for various reasons, believe that at least some such objects do possess meaningful analogues of thought and feeling, and may be in some sense invested of a soul.
Perhaps the most extreme philosophy is that of panempsychosis, which holds that everything is literally alive. There is some variation in how one defines "everything", and whether parts of wholes qualify (does the corner of a brick have its own life separate from the brick itself?), and whether collections of discrete objects (does a pile of bricks have an identity as a living thing separate from the bricks that make it up?) Regardless of the details, though, there are those who really believe that every object (by some definition of "every object") is truly in some way a living thing. One argument that has been advanced in favor of panempsychosis combines the principles of hathroics and tyctothymy: if one accepts hathroics as valid, then surely a cosmos is alive, or at least a universe, being a self-organized system of sublime complexity. But then there is a sense in which the cosmos, or universe, creates everything within it, so if one accepts tyctothymy then everything within the cosmos or universe in question must be a living thing. (Dissentaneous philosophers have attacked this argument on many grounds, but panempsychotists seem undeterred.)
Despite its apparent outlandishness on most worlds, there is one cosmos in which, remarkably, the claims of panempsychosis are demonstrably true. In the cosmos of Dhaya, every object (and, subject to certain qualifications, part of an object) corresponding to a whit that is a fully living being, though probably the vast majority of these whits possess little more intelligence or sentience than a bacterium. Still, the fact that it may be factual in Dhaya does not prove that panempsychosis has any real validity in other cosmoi.
Origin and end
While there are those who believe that some planes and cosmoi are without temporal beginning or end, no sure proof has been found of any such thing. Indeed, most known universes can be traced back to a probable beginning point. There was a time before the evolution of the godworlds when the Sacred Sea was a fluid-filled plenum. There was a time in Charos when dream magic did not exist, and before that when the worlddisks themselves had not yet formed. And there was a time when all Tamamna was fantastically compressed before it burst forth in the Big Bang. Except for committed panempsychotists, anyone will agree that in all these cases, the universe began with no life in it. The question of how life first formed is called abiogenesis. It is a complex matter, but almost certainly stems ultimately from the fact that life exists along a continuum. There was no sudden transition from lifelessness to vitality; rather, a few simple structures formed with the ability to self-replicate, and their products and their products very gradually complexified and very gradually took on more of a semblance of what could be called life. When, then, the first living thing appeared is not a question that can be unambiguously answered; it depends on where one subjectively chooses to set the threshold of what counts as "living".
Separate from the question of when life itself first entered a plane or universe is that of when a given life form first comes into existence, or first becomes alive. This, too, is an indefinite matter. In the case of a biotic organism, even if one considers a single cell to be a living thing, the question remains of the status of the two zygotes that merge to become the cell. (The matter of when an embryo can be considered alive is, of course, a separate question from when it can be considered conscious, or when it can be considered a full-fledged member of its parents' species.) Then, too, setting aside the incipience of life in a newly born or created entity, one could also ask when a newly developing life form really becomes a distinct entity, separate from the parent it's growing inside. While the moment of birth is a convenient event to begin counting from, it doesn't necessarily mark the true incipience of life.
If the beginning of life is hard to define, the end of life—or death, as the cessation of life is called—occasionally can be as well. This is, of course, not always the case; if a living thing's body is incinerated almost instantaneously by intense heat, for instance, its time of death is clear. But often disease or disability leaves an individual lingering between life and death for extended periods, and even in such apparently clear-cut cases of death as decapitation there are claims of severed human heads retaining consciousness for several seconds after the fact—and in the case of some animals such as cockroaches and even chickens, the headless body may survive for extended periods before it succumbs to starvation.
Paradoxically, on magical worlds the death of the body may not be the end of life. Some dead may linger on as undead, either still retaining some control over their original bodies or as intangible entities. In many cases, all the dead, save perhaps those who perish through certain exotic methods, persist as disembodied or reëmbodied souls, either being reincarnated into new lives, passing on to some eschatological plane, or perhaps being absorbed into some greater whole. Furthermore, there may be means—not just magical but perhaps with sufficient access to medical technology as well—of bringing the dead back to life, though on most worlds even where such possibilities exist they are rare and difficult.