Many anarchists assume that because the anarchist movement has been around for a couple hundred years, it'll be around in the future. This is not at all guaranteed. My own project bets very strongly on its continuation, but I want to make the argument explicitly.
I've written about the sociology of anarchism as a movement and philosophy / ideological ecosystem. How movement dynamics sustain and influence ideological directions, and how different channels of recruitment operate.

http://humaniterations.net/2018/01/29/sociological-entrypoints-to-anarchism
By the anarchist *movement* I mean something socially coherent (with culture, institutions, networks, infrastructure, etc) and distinct in some sense from "the left." Examples of plumbline anarchism at the center of the "movement" would be Crimethinc, IGD, Graeber, & Gelderloos.
Now, let's look at some ways anarchism could end. I see roughly three main endings: 1) Evaporation into background assumptions. 2) Forking into distinct competing movements/philosophies. 3) Outright extinction.
Evaporation is a conclusion I don't think enough people think of. Once upon a time things like republicanism and democracy were intensely marginal and radical movements, but they grew into generic acceptance to the point where they're meaningless terms and non-movements.
This isn't to say that the evaporation of anarchism would involve the fall of the state -- we could instead imagine a world where virtually everyone of every flavor asserts their enmity to the state and desire to transcend or end it... and yet the state is maintained.
( Imagine a future where members of congress on opposite sides positively cite Rothbard and Kropotkin. Oh wait, we're already there, lol. )
One way this can happen is everyone goes through a stage of active involvement in the anarchist movement & then drifts into normie life without a moment of conscious renunciation. So you get anarchist social workers, plumbers, etc, who just take assumptions/values as background.
The second category of paths, Forking, involves sectarian, identity, cultural, or philosophical splits in anarchism growing to the point where completely different core philosophies and practices diverge and general solidarity, social connection, and common discourse dies.
To some minimal extent we saw this with "anarcho-capitalism", but the ancaps never really built a *movement.*

At their height they built a mildly popular online identity for a few minutes parasitic on right-libertarianism and then saw tons defect to fascism et al.
Moreover "anarcho-capitalism" was always an external project. It didn't emerge from *within* the anarchist movement, Rothbard was just like "lol, those fuckers must of died off in the 40s right, let's steal the term from their grave, they're not around to care."
Probably the greatest split in the contemporary anarchist *movement* remains the red v green split, which *does* involve cultural/social clumping. But what mostly happens isn't the splitting of anarchism as a movement, but the abandonment of anarchism by the furthest partisans.
Largely this is the reds, in part because distinct socialist & authcom movements exist for them to defect to.

This partially sets up a linear progression whereby "intro" anarchism is red (because mass recruitment) and then if you stick around you go green ("advanced" anarchism).
But while smaller in number there are defections on the green partisan side too. See the emergence of "nihilism" and "postanarchism" in the last couple decades as a few folks so inclined have even explicitly renounced anarchism. Also a number of ecofash et al defections.
The hostility between reds and greens has always been there, but the anarchist movement as a whole hasn't *split* as a consequence. There resolutely remains (at least for now) a kind of common center cluster of overlap/contact, with diverse branches growing outward from it.
Finally there's the possibility of full on ideological extinction. So for example every single person is like "lol that was an obviously mistaken take" and anarchism never again leaves the dustbin of history. Or like you know, we're all killed off in The Collapse or whatevs.
But even if anarchism *is* objectively mistaken I think this sort of ideological extinction is virtually impossible without a truly massive global wave of repression or collapse that exterminates anarchists and makes anarchist material inaccessible for at least a century.
I *am* worried about such a possibility. I focus a lot on how to preserve anarchist thought during systemic repression, rebuild society after a horrific collapse, and keep networks of communication open as wide as possible. But all that is relatively simplistic.
The real question in my mind is over anarchism dying of evaporation or forking. Why would there persist a central cluster of "anarchism" of some variant that is self-aware enough to maintain its own discursive history? In other words will contests over "anarchism" today matter?
My own perspective is basically plumbline anarchism plus a few corrective tweaks (albeit hugely contentious) around markets and technology.

But why stick with anarchism? Why struggle so hard to influence the anarchist movement specifically rather than other folks?
The general case for focusing on anarchism is 1) it has a rare concentration of some of the most altruistic/sincere people in the world in terms of values, & 2) while it will never "take power" it's the site of innovations and ideas that consistently influence everything else.
Yet if anarchism as a movement isn't long for this world it might make more sense to try to influence discourse in academia, effective altruism, libertarianism, socialism, etc... Am I merely attached to anarchist circles and discourse because I came up in it?
I do think the anarchist movement is around for the long term. Long enough at least for me to be proven right about a variety of things. (If you're not in part playing to future historians and future discourse, you're not as incentivized to be ultimately right.)
While I was coming up in the anarchist movement I often felt extreme frustration with it, but over time -- in part as I've seen many terrible but once internally popular takes die out -- I've flipped to being something of a reactionary defender of the existing movement's value.
This has come to a head as the internet decided to treat leftist ideology as the ultimate fandom and ideological identification got suddenly widely disconnected from in person movement infrastructure and social pressures. I've done my whining about this turn from the *movement.*
We joke constantly about the internet's proliferation of ideological signifiers in a disconnected jumble, but while some channer folk may feel that everything is in flux now, an acid sea of ideological positions, eroding uniquely concentrated points I think they're just wrong.
I don't it's an "everything is up for grabs, nothing is fixed anymore" situation.

Firstly, I think certain points in ideological or philosophical phase space are more stable. There are certain root dynamics that pull & accumulate. I've written about this: https://c4ss.org/content/50888 
Now may also be true that there are severely different underlying philosophies someone can collapse to from a superficial "anarchism" -- eg the sort of freedom taken as ultimate value by a wildist or a transhumanist is gonna diametrically differ, obviously.
There are certainly a host of vastly different competing philosophical positions setting themselves up as competitors to claim the root of anarchism. Another example is a kind of quietism that takes negation to desire, self, etc.
But secondly I think the sociological dynamics that give rise to the anarchist movement are pretty much not going to change. This is part of why, when certain camps advocate a redefinition of anarchism that rejects activism and struggle, I just laugh at their prospects.
I've talked about The Left as a kind of "pluralist coalition of underdogs" to differentiate anarchism *from* The Left. But anarchism as a social phenomenon is pretty inextricably tied to the sociological dynamics of The Left. We're distinct but parasitic on it, in some sense.
Although there are a variety of channels by which anarchists are made, the overwhelmingly central one is activism, and *will always remain* activism. In this sense "activism" as a movement or milieu or body of people is eternal in a way that the specifics of today's left aren't.
Altruistic people will see people getting oppressed and want to struggle against that, they can either do that in a slapdash ad hoc pluralistic and contradictory way -- via The Left, or they can attempt to get more consistent, coherent, and radical about such value / inclination.
Once you shift from happenstance or historically contingent oppositions to specific lines of domination and shift to fighting ALL domination you're going to arrive at plumbline anarchism.
And so long as there remains even any appreciable numbers of anarchists in the activist milieu or engaged in wider struggle, this is where the vast majority of anarchists *who matter* will get minted.
(I'm inclusive of some kinds of online "activism" here because as Sunde put it "the internet is the real world", and also while much of the internet explosion is currently disconnected from the traditional anarchist movement, that's kinda resolving over the last few years)
Anyway by both sheer numbers and influence the activist, altruist, and practical anarchists will always constitute a huge plumbline base of anarchists. And this tempers the sectarian fights, creates a center of gravity they/we have to play around.
Someone goes "anarchy is really about rejecting struggle to instead go off and start a land project and never talk to anyone" or focuses on academia and cool, they're immediately irrelevant. They will not shape the future center of mass of the movement.
(Except by evaporative cooling. The creation of burnout channels for certain tendencies or inclinations can influence who stays. So it can matter that there are folks who abandon anarchism but keep publishing communiques because they forget how to do anything else.)
In recent years a few burnout paths have presented themselves as in the post counterglobalization era veterans explored potential deeper philosophical foundations to anarchism.

Incoherent Negation. Wild Nature. Quietism. Positive Freedom. Obviously I'm a partisan of the latter.
All of these projects seeking to extra ground anarchism are at a kind of remove from the practical activist plumbline, but there's differences in how resonant or dissonant they are with the core recruitment pathway for anarchists.
Quietism has probably the most ridiculous prospects. You can't really expect bushytailed altruists hungry to struggle against oppression to overwhelmingly shift over to embracing rejecting desire. It's a minor burnout path, sure, but will never eat "anarchism."
The other two are pretty doomed, provided the conditions for activist struggle of the crimethinc, IGD, or even 325 style are still relevant.

But there are changes that could cause them to win out and entirely eat "anarchism" or cause a real fork.
Basically the path to scene hegemony for incoherent negation is a getting locked in a deeper totalitarian hellscape where activism/struggle is almost entirely destroyed as a recruitment path & all that's left is inchoate revenge.

Where everyone is attackyattack without strategy.
Insofar as strategic considerations are still in play, with goals, values, models, plans, etc, the movement is inevitably going to bend back towards rationality, critical thinking, etc, and away from the proud incoherence of "negate everything."

Same as it got bored with woo.
(There is a related danger that the Two Cultures War will polarize political discourse into "rationalist/analytic" vs "postmodern/continental" discursive worlds further to the point where anarchism cracks in two with the core moving negationist... and then dying out.)
Mostly for proudly incoherent negation to win out as the hegemonic definition of anarchism (and consequently albeit slowly cause anarchism to go functionally extinct), the world has to become so that grim strategy, rationality et al are impossible to even think of.
And such a future doesn't have a future for anarchism in any substantive sense, much less as a discourse, it'll be an extinction end where all that's left of anarchism is but stray whispers between the few suicides throwing themselves fruitlessly on the gears.
The path to scene hegemony for Wild Nature is harder. Yes, we're facing ecological collapse, but struggle is kinda inherently progressive & radical, it's hard to reconcile with reactionary & essentialistic arguments. Tucker's all in on "human nature" now; it's not a winning card.
However, IF we see near universal social/infrastructural collapse to smaller communities (eg in a balkanization of the US or permanent civ collapse) I suspect that essentialist "this is why" reactionary arguments will surge (also the "national anarchist" nazis will surge).
This is the pathway where we see evaporation of "anarchism" -- so many varying tendencies would identify as "anarchist" and gain number/enclaves, from neofeudal ancaps to ecofash etc, there'd be no common movement remaining. Also no internet/connections = no common discourse.
In this future "anarchism" becomes a completely empty signifier of "good thing" with no coherent or common thrust, much as "democracy" functions today, championed by both Trump chuds and Demand Utopia nerds. Infinite multiplicitous definitions to meaninglessness.
But humans are ingenious buggers and there are at least odds we won't see *complete* collapse or *complete* totalitarianism, and thus standard activist channels will generate a single mass anarchist movement of roughly the same character.
(And also, lol, in any case IF we see total civ collapse or absolute totalitarianism, there's dramatically lower odds of anything I care about being possible, and also no future historians of anarchism to judge how I was Right All Along, and thus impact more positive directions.)
Further, even if things get *a lot better* (lol, stick with me), even if we get to the point of some broad global libertarian socialism that claims "anarchism" in shallow terms, the activist/struggle channel will remain and so will the anarchist movement.
Because even if there are magical communes everywhere and broad social enlightenment, there will still be tons of persistent dynamics of domination to be fought against, and "anarchism" sets itself in furthest conflict against them.
Basically -- in summary -- the "activist" dynamic (insert insurrectionist, mutual aid, etc if you hate some of that term's associations w/ managerial organizationism) that what a certain corner derided as "strugglismo" will always exist & strongly define anarchism as a movement.
This is the source of problems as the activist base is partially more "leftist" than "pure" anarchist, in the sense of being more "underdog pluralism" than anti-power, which means that what it makes hegemonic or central in anarchism will be sometimes skewed. But...
It is also a corrective influence in that it has channels that sustain it in numbers and passion, which severely divergent boutique variants of anarchism do not by themselves.

They can function as burnout or "level up" paths, but can't strike off independently on their own.
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