Unity is the white whale of leftist discourse. Any argument between leftist groups any perceived sectarianism will be met with demands to shut up because you’re ruining leftist unity. Left unity appears to be something that is just beyond the grasp of leftists to spoil the ending of this that is because left unity is bullshit.
At this point, I should probably talk about what left unity is. Usually left unity is a call for unity of praxis which generally means in action. People are essentially calling for leftists to put aside their ideological differences, which I will be getting to, to organise against capitalism. This is why leftist in-fighting is often met with a strong reaction as it is seen as dividing and weakening the left, thus making the overthrow of capitalism a more difficult task than it already is. Left unity can, more rarely, be used to mean uniting people with regards to specific issues where the solution and method of implementing that solution are agreed upon.
At least instinctively this unity seems to be a good thing. After all, as Abraham Lincoln famously once said, “A house divided against itself cannot stand." if leftists have a shared common enemy in capitalism. In that case, it will make sense to seek a unified movement which would be far more powerful than any individual leftist sect.
The problem with this approach, however, is that it treats the left as a single house when, in reality, the left is more of a loose collection of houses. The left is composed of a series of highly individualistic groups built around individual social and philosophical critiques with different practical approaches to solving these critiques. On the left, you will find reformist and revolutionary socialists; utopians and scientific socialists; anarchists and statists. Calls for unity often ignores the diverse spectrum of political thought that the left truly is.
Not only do calls for left unity unintentionally treat the left as a singular entity with a unified means and a unified goal, beyond overthrowing capitalism that is, calls for left unity actively seek to impede the greatest tool at the disposal of leftists generally speaking which is the exact disagreement on tactic and philosophical outlook that is derided as divisive and damaging to the left as a whole. That isn’t to say all conflicts between leftists is productive the bad faith name-calling and caricaturing is at best useless and at worse actively damaging. It is to say that it is through the open debate on praxis and theory that the left can develop and innovate. This lack of unity is hardly a new phenomenon on the left either Karl Marx himself got himself into frequent arguments with leftists writing scathing critiques of the works of Lasalle and Bakunin amongst pretty much any leftist who threw their hat into the ring. He wasn’t the only one, of course, Bakunin gave as good as he got and Marx was routinely condemned by pretty much every socialist and communist organisation in Europe. Rosa Luxembourg a socialist, who gets so little attention in socialist circles it borders on a travesty, picked fights with anarchists, market socialists and state socialists. My point being that had leftist unity been pushed for in these days we likely would never have developed marxism as an analytical framework in the first place and would be left languishing in the days of the utopian socialism of Owen or Saint-Simon. It is only through constant good faith infighting that leftists can address our past failures both theoretical and practical and improve upon them and through that continuous evolution of socialist thought lies the most substantial chance for leftists to succeed.
Setting aside the idea that leftist development and innovation hinges upon leftist infighting, there isn’t anything that different groups of leftists can unite on. It is true enough that unity in the context of local material problems between people who agree on how to solve it is a good thing, but this is almost a non-statement as that unity already exists and does not need calling for. With some exceptions, leftists generally have one final global goal that is agreed upon. That goal is a workers revolution to overthrow capitalism. Leftists may be agreed on this broad goal; however, leftists can’t unite under it if they have opposing goals and different methods of achieving those goals. A revolution made of people who have vastly different and opposite plans will never have a coherent view of the society it wishes to bring, and a revolution without a cohesive picture of the society it hopes to institute is unlikely to garner mass support. It is even less likely to achieve anything of meaning.
Does this mean that I think unity is a dumb concept that people should stop seeking? Partially. People should stop seeking to unite on the basis that they are on roughly similar parts of the political spectrum and we definitely should not be collaborating in a sense that our disagreements should take a backseat. So what should we do? We should be doing what leftists have always done standing in solidarity with workers against capital standing in solidarity with the marginalised against their oppressors. We should be taking direct action with whoever our methods and end goals align with, and we should be engaging in a constant discussion as to our methods and ideologies. The power of leftist groups has always been the local organisation to tackle the issues facing the community that a leftist group finds itself in. We can collaborate on problems locally without suppressing the rich and diverse range of leftist thought.