So I imagine there may be more than one alternative to solipsism within subjective idealism, and if so, others might elaborate on their number. However, there is one, what I feel is an obvious alternative, and I want to discuss it, and how I think it relates to solipsism, and why this alternative has utility for me. I’m hoping if it’s not useful to someone else, may it at least be entertaining.

In subjective idealism there are only two “hard” requirements: subjective and idealism. Subjective means perspective is fundamental to what we’re talking about here. And idealism means the mind or the mind-like (volitional, for example) nature of reality is also important. So right away we can see nothing here is talking about how many perspectives there might be. Nor do we see anything about what might a valid perspective be, or what a valid grouping or intersection of perspectives might be or look like. So this, in my opinion, leaves us with a fairly wide field to play on.

So in my view the main difference between the various flavors of subjective idealisms will be in how the perspectives are configured.

If we emphasize a single subjective perspective, we get solipsism. If we emphasize some (perhaps infinite) multiplicity of subjective perspectives, we get another kind of subjective idealism. This latter emphasis is still fully within subjective idealism because: a) all perspectives are held to be subjective, and b) any cross-referencing of these perspectives or the overlaps between them are still subjective. And of course, we can still maintain that mind (the threefold capacity to know, to experience, and to will) is the foundation of everything known and unknown, experienced, and unimaginable, so we’re still left with subjective idealism.

So by emphasizing multiple concurrent subjective perspectives we get a subjective (non-neutral!) middle ground. We could call it an intersubjective space. This intersubjective space is just as optional and therefore just as subjective as anything can ever be, even if it’s multilateral. So simply speaking, if one million people say strawberry is the best berry, that’s still subjective, regardless of how many people say/experience so.

I think the main practical difference here is that by emphasizing multilateralism, you’re giving up some internal power, but in exchange you gain a sense of a wider world, the kind of world where you can lose yourself.

With a solipsistic emphasis the center of gravity is always in your own perspective, and whatever other perspectives there may be, they’re unimportant accessories that revolve around your own perspective, caught in its mental gravity well. Anything crucial and important is done entirely internal to your own point of view in this configuration. And importantly, only your own point of view serves as the foundation of confidence and validity. So, if I feel it’s cold, and a thousand people say it’s hot, what the people say is not important, but the important thing is that I am experiencing cold. In this configuration I can really stand firm with both feet inside my own perspective and there is no need to cross-verify myself with any other perspective. So I don’t need to ask people, “Do you see what I see?” Etc. This is what allows one to develop immense concentration: there is no need to worry about how something looks or feels from outside, as it were, so one can focus every effort internally and one controls everything necessary for confidence-building.

In a multilateral setup you have to surrender some of your validating power in order to allow other people to have input on the “same” experience you’re having. Because of this, multilateralism, except in trivial cases, does not ever allow 100% confidence to be generated completely internally to a person (observe the importance of peer review in the scientific process). Whatever I experience internally, until I discuss it with others and make sure they’re all experiencing things in the same way, I can’t be 100% confident in what I am doing/experiencing. In trivial cases this is avoidable so that I don’t need to verify with others that I am really walking up the stairs when I think I am, but for anything interesting and non-trivial cross-verification is unavoidable under a multilateral approach. So this makes personal confidence a distributed system where you aren’t in control of your own confidence. This reduces one’s ability to maintain deep concentrations, because at every point of experience, especially when it’s strange (and deep concentration results in strangeness), you’ll want to verify that whatever you’re doing/experiencing is valid from other people’s POVs as well. So you can’t go alone, wherever you’re going. In a multilateral setup you either have to stay with a group, or you have to drag an entire group with you to make yourself feel validated. This would explain the desire of some religious people to force their religion on others, btw.

In a multilateral setup one perspective is not sufficient to narrate experience. In a multilateral setup experience is narrated collaboratively, communally, together.

So I see it as a trade-off similar in kind to what engineers like to talk about. If you move the center of gravity inside your own perspective, you then have everything you need for limitless confidence, since you no longer need to consider any other perspective, and your life is no longer a “design by committee” life, as it were. This is powerful. However, precisely because personal influence is greatly expanded, the whole world can start to feel really small. You might feel like a whale in a teacup, eventually.

In an attempt to have my cake and eat it too, I’d like to teach myself to be able to pivot my mind around a number of similar and related views. If I need a vast and total transformation now, and I don’t want to wait to build a consensus, I want access to solipsism. If I am OK only directly influencing my back yard, so to speak, and if I am OK slowly building consensus, and not feeling like I am solely responsible for everything, and if I want to feel like I live inside an infinite world, as opposed to a teacup, then the multilateral setup is much better, and I’d like to be able to pivot to it, especially when the times are good.

And that brings me to another aspect: responsibility. In a multilateral setup responsibility is shared, which in some sense is a load off one’s shoulders. In a solipsistic setup if I don’t like something, I can only complain to myself. So solipsists are in some sense perpetually trying to lift themselves by their own bootstraps, and this has all the familiar advantages and disadvantages. As someone who pivots toward a multilateral perspectivalism it is completely valid to solicit and expect help on any number of issues.

So this ability to solicit and receive help in a meaningful way, is also a gentler, more gradual, smoother interface between subjective idealism and the more conventional modes of thought such as physicalism and dualism. And there is, in my opinion, definitely something to be said about a gradual, step-by-step, degree-by-degree approach. Going from physicalism straight to solipsism would be a very difficult and severe turn around that would put a lot of strain on one’s mental constitution.

So if something is difficult to do all at once, and there is a gradual option, I definitely like that. I think even if someone viewed solipsism as a kind of end-point for subjective idealism, even then, even in this case multilateral perspectivalism could represent a reasonable step to make, something that’s much more realistically doable sooner rather than later.

In summary, I think the advantages of a multilateral perspectivalism are that: a) it paints a wider world, the kind you can lose yourself in, b) you can meaningfully solicit and receive help and share responsibility instead of owning everything yourself, c) it’s a more gradual transition from more conventional worldviews.