Platformism is a school of thought within anarchism developed by Nestor Makhno in response to his experiences with the Free Territory in the Russian Civil War and its eventual defeat at the hands of the Bolsheviks. Platformism is a theory that it's built around anarchist organizations that focus on unity. This means that everyone in the organization has the same general theoretical beliefs (so everyone is an anarcho-communist or everyone is a mutualist, though with more specifics than that, rather than combining a bunch of anarcho-communists with a bunch of mutualists), the same general tactics (so everyone is committed to, say, non-violent protests or to syndicalism and a general strike, and not a combination of people committed to the first and people committed to the second), everyone shares a collective responsibility in the struggle (this is the part I least understand the details of), and the groups are organized together through federation as we wish to see after the revolution rather than separate from each other. In addition, they tend to focus on outreach to non-anarchists and spreading the anti-authoritarian ideas as far as possible so that the revolution will have sufficient participants to be able to defeat the state.
Now, there are two general criticisms I can think of surrounding platformism. First, all the talk about "theoretical unity" or "tactical unity" sounds pretty authoritarian, like forcing everyone to believe the same things. However, this criticism ascribes to platformism methods it just doesn't advocate. It doesn't say we should force people to all believe what we believe. Rather, it says that the anarcho-communists should gather in a group and make it a basic requirement for joining the group that one has to be an anarcho-communist. This is not all that different from, say, not letting leninists join an anarchist group.
Second, this group sounds suspiciously similar to the leninist vanguard. Are you sure that Makhno wasn't just convinced of the effectiveness of the vanguard by being beaten in by the Bolsheviks and became a crypto-leninist? Well, no. Rather, he became convinced that anarchist organizations previously, including ones he was a part of, were ineffective at combatting powerful enough states, including ones lead by leninist vanguards. Thus, anarchists needed to rethink things if they wanted to ever defeat the state. However, rather than borrowing leninist ideals, he decided that two things were necessary: unity and numbers. If we all fought together with the same goals and the same tactics, we'd work together far better allowing us to counter state power more effectively and, if we had lots of people, we'd have more people to fight the state with. You can see this in the two aspects of platformism. The talk about organization is all about unity and togetherness, while the talk about tactics is all about getting as many people as possible to become anarchists.
Those were general critiques from anarchism. There are three additional ones from specific branches of anarchism. First, the synthesist/AWA/panarchist critique, why can't we all just get along and work together? I mean, we all want to abolish the state and capitalism, can't we focus on destroying those and focus on what comes next when it comes to that? I mean, if there are more of us, surely we'll be more effective. This is the argument I find most convincing. However, I still see the platformist's point. If we're all different types of anarchism, we will be less effective because we'll constantly bicker among ourselves. In addition, how motivated would a mutualist be if everyone else was an anarcho-communist? Certainly not as motivated as if everyone else was a mutualist. In addition, if we all agree, in general, on what we want after, we can better convince people now because we'll all be arguing for the same things, so no one will be arguing against what others in the organization are arguing for, so it would hurt our ability to get a lot of people. Thus, unity of theory and tactics, not diversity of them, is better, to the platformist.
Second, a post-left/insurrectionist critique, why do we need to be so organized? It comes back to unity. This time, unity of action. If we organize ourselves, rather than acting individually or without much organization, we can all act together as a united front. This creates a strength in numbers sort of effect. One person facing a police officer will be less effective than ten people facing a police officer. In addition, ten people who don't know what each other are doing and don't have some sort of plan facing a police officer will do worse than five people with a plan (or at least general plans for how to deal with such situations) who move together against the police officer.
Third, another post-left/insurrectionist critique, why do we have to wait until we get a lot of people? Why can't we revolt *now*? Because the state has a lot of manpower and a lot to make that more effective, eg tear gas and advanced weaponry. In addition, oftentimes someone rebelling small scale can turn the ignorant away from anarchism before they learn anything about it, causing them to see it as a violent and brutish ideology because they don't know of the violence, brutality, and oppression of the state that necessitate fighting back. Not only is fighting with more people more effective, fighting before we're ready can keep more people from joining us. That's why we need to educate and promote anarchism, expanding our base, before we do a revolution.
Now, all that being said, I'm not a platformist. Why am I not one, given I've rejected every criticism of it I've presented? Well, while I don't think it is bad, I also don't think it is *necessary*. Quite frankly, I'm not convinced by the arguments that previous anarchic organization is necessarily ineffective at combatting the state. I'm not convinced that the Free Territories were crushed because of how they were organized. Rather, they were crushed because Russia is big and Ukraine is small. The people of Ukraine could've effectively won against the Ukrainian state, but the Russian state had far more people to call upon, so they stood no chance, regardless of how many Ukrainians had joined them. While I do find an appeal in platformism, and I find their arguments for unity persuasive, I also find the synthesist arguments for unifying many forms of anarchism persuasive as well. I would, personally, be more than willing to join up with platformists or sythesists.