Definition is a subtle and difficult art, which would benefit from case studies or specimens.
Definitions are handles. You can't grasp Reality directly. It's too big. Hence, you bolt handles to Reality and grasp the handles instead.
By thinking about the handles explicitly and practising with them, you can arrange your handles neatly and harmoniously, making your own thoughts clearer and easier to think.
"But I'm not seeing reality! All I'm seeing is these handles!" You could never grasp reality, so it was always only handles. The question is whether you try to force the handles to be something they're not, or let handles be handles. You can get away from the puppet-shadows others show you, but it's impossible to get away from the shadows you show yourself, aka your own thoughts. As it turns out, that's good enough. Let the shadows be shadows.
Having played around with your own handle arrangement sufficiently, you can easily understand others' arrangements of handles, and be easier to communicate with. You can also see their messy, incompetent handle arrangement, and how it leaves open spots that are big enough to be a problem but too small to bolt in a new handle, thus making it impossible for them to understand certain important ideas.
Doesn't that sound exciting?
Because politics, the handle 'religion' immediately becomes corrupted. It's deliberately placed in an offensive position. You should be offended, and reject it.
Ultimately the handles you use must be useful to you. Useful handle placement is not up to you, it's up to the shape of your underlying system of needs, and secondarily by relation to the other handles you're using. Even if you use some weirdo definition of "religion" on the outside, it's important to use a good definition internally.
What is religion?
Handles, ultimately, can be carved into whatever shape you want, subject only to the restrictions of shape per se, such as the fact there are no circles with corners, and the fact that the shape you make one handle defines the open space next to it.
Atheists like to say religions are inherently supernatural. They then have no choice but to admit of a second handle which is exactly like a religion in every way except with no supernatural tenets. (I will be specific later.)
Many Christians also like to say religion is inherently supernatural in a way that conflicts with good epistemology and tends to leave them defenceless against religious persecution by atheists, since they can't correctly name it religious persecution.
"directly from Latin religionem (nominative religio) "respect for what is sacred, reverence for the gods; conscientiousness, sense of right, moral obligation; [...] or "bond between humans and gods.""
As a matter of empirical fact, humans treat religious matters specially. I find general knowledge of these things is, surprisingly, accurate. Fundamentalist religion is real and acts like popular conceptions of fundies. Religious things aren't supposed to be questioned. I find the relevant distinction is between particularist religion and universalist religion. Religions that say you can be right about your religion without disproving mine, and ones that don't. (P.S. Universalist religion is narcissist.)
What we want, then, is a description which accurately diagnoses religious behaviour as religious. Ideally, having listened to someone's customs, we'll be able to predict what they're apt to get activated about.
It turns out it's incredibly simple: a religion is a comprehensive code of behaviour. A big 'ol lists of oughts.
We're most familiar with the "You ought to behave as God says because God is great," form of the religion, but almost anything can stand in for God in this formula. "You should do what popular opinion says." "You should do what the king says." "You should do what Science says."
Because of this, there's a super quick-and-dirty religion diagnosis: if a system has an opinion on something a known religion also has an opinion on, then it's also a religion. Generally it will have a different opinion and thus be a competing religion.
Religions will always form taboos (ought nots) and rituals (demonstrating loyalty to the oughts). In general they'll have a Pope because Popes are possible and someone will try to seize the spot.
Generally speaking a religion will become culturally ingrained. Questioning aspects of the religion are equivalent to saying someone has been living wrong their whole life. Getting them to accept that is a big ask, especially if the major effect will be to piss off their neighbours by acting funny.
Having a decent description, we can immediately see that atheism adds special bits onto their idea of 'religion' for reasons of illegitimate stealth. It seems they're dimly aware of the true description, as they also like to deny they have a code of behaviour, despite the empirical difficulties. It's a comprehensive code of conduct, which consequently can't be meaningfully questioned, rooted in something other than the sacred. All their criticisms of religion are rooted in properties they themselves partake in.
Likewise, Christianity wants to make itself out to be special in a way that it simply isn't. "My great spirit is greater than your great spirit." Yeah yeah well I can eat fifty onions and my dad can beat up your dad.
In both cases, part of the code is to loyally pretend to misunderstand what is being adhered to.
Having a decent description, the usual habits of the phenomenon hardly need explanation. Clearly the religion will get tied into the ego and become dogmatic. Something you do becomes something you are. Etc etc.
https://en.wikipedia.org/wiki/Raven_paradox First, let's back up: what's a "raven?" Can they even be non-black? It depends on how you define it.
If you define ravens as, among other things, a bird whose feathers are black, then you'll find that non-ravens sometimes hatch from eggs whose parents are both ravens. If you get lazy and definite as a bird with black feathers, then you can stop a raven from being a raven by plucking it.
Fun fact: if you define ravens genetically, you get similar results. E.g. bombard the gamete with radiation, and they'll mutate enough to miss the definition. This can also happen non-artificially. Alternatively, you make the genetic definition so fuzzy that sometimes ravens are born from two parents who aren't ravens. If you define a raven as an entity which has two ravens as parents, then you've only pushed the question up a level. Formally begging the question.
There is no definition of "raven" which includes every instance of a raven born to raven parents, and no non-raven born to non-raven parents, except the degenerate definition explicitly listing every individual instance of raven babies. This is a consequence of the fact that all measurement devices have some margin of error. Infinite accuracy is impossible because infinity is impossible. The linguistic description of a raven is not a raven itself. The handle is a handle, not reality itself.
(Bonus round: a definition made of an explicit list is trivial to game. "Every raven is a raven and is entitled to raven rights - except that one." Unmistakably this is sophistry, but sophistry works. Try not to, at least, make sophism easier.)
However, with definitions, accuracy is beside the point. Having made a definition, it includes itself...by, uh, definition. A certain amount of effort spent to keep the definition from being too intuitively dissonant is good, but don't get trapped trying to get it exactly the same.
You can decide your definition, but you can't decide the consequences of your definition. If you define a raven as a feathered, winged biped, it will be able to fly except in truly exceptional edge-cases.
In practice, definitions are not that hard to get good enough, the same way you don't need triangulating laser interferometers with caesium clocks in most cases. A ruler stick will be fine. The good-enough definition pivots on the meaningful property. What are you using ravens for? If it's pie, then [flying meat thing] is close enough.
If you want, you can define a raven as being able to fly, if flight per se is important to your purposes. You will have to match it with various pseudo-ravens, such as raven chicks and ravens with broken wings, to cover the full spectrum of observations, but it's not like it makes a full set of handles impossible to carve. It's mainly a question of which set of handles is the least hassle to grasp.
As a matter of practice, Darwinian/Linnaean definition uses a type specimen and then asks what other specimens are related more closely than some arbitrary bound. This is close enough to the meat-based peasant definition. No, not all ravens are black.
P.P.S. Philosophy, roughly, is the religion of questioning everything, including the precept of questioning everything. Hack the sacred by going meta. If the sacred is damaged by questioning, clearly questioning >> the sacred, and you made a mistake. Questioning is clearly more sacred than things-previously-known-as-sacred.
Nevertheless once a sacred thing has survived the alkahest, analysis, it ought to be respected in some way or another. I'm not 100% clear on how this works.N.B. The idea of asking questions is to get answers, not to ask questions. Answerless questioning is degenerate; profane profanity.
P.P.P.S. Defining 'artificial' is a useful exercise. Spoiler: artificial is a useful category, especially for its opposite, but its opposite isn't [natural], because [artificial] is a subcategory of [natural].
P.P.P.P.S. Self-correction: Plato's cave analogy breaks down when it comes to the mind. You are the shadows. In fact there was never a fire or puppets or a cave, Reality was all shadows the whole time. Reality is made of your thoughts, logic is the fact your thoughts are related in strict ways, and that's it. Wisdom, ultimately, is prosaic, not profound. It's about arranging input thoughts to create pleasing output thoughts. We call the fact that some thoughts are not under our direct control [the external world].