However, I do actually believe in the unity of the Universe; what I doubt is the ultimacy of any objective means by which it can be comprehended. — Wayfarer

The problem I see here is that you're contradicting yourself; by saying that it is a unity you are claiming to be able to comprehend it.

Perhaps you will say that you comprehend it, not by objective means, but by subjective means, but then that would entail that the unity of the Universe is merely a subjective opinion. Others may not comprehend it that way, and have other opinions, in other words.

If you are merely stating what is your own personal feeling about it, then that's fine. But to want to extend your own personal feeling to become something universal is where the problem lies. Of course we all do that, it is the inherent nature of aesthetic judgement to do that, which Kant pointed out in his third critique. Ironically, in a way you seem to be attempting to objectify your judgement that the Universe must be unity. And that is inevitable, because if the Universe is a unity, then it really is a unity, that is the fact of its unity is objective.

by saying that it is a unity you are claiming to be able to comprehend it. — Janus

I sense it, but I know it can't be proven. But I think the term 'universe' has significant meaning in its own right; the Greek term 'cosmos' means 'an ordered whole'. But that sense of an ordered unity is conspicuously absent from modern cosmology, what with the multiverses and parallel worlds and so on.

On a related note, the subjective unity of perception is intuitively obvious; but how that arises, is still a mystery to science.

Perhaps you will say that you comprehend it, not by objective means, but by subjective means, but then that would entail that the unity of the Universe is merely a subjective opinion. — Janus

Here's the thing. Objective and subjective are both part of a greater whole, because subjects arise in a landscape, or an environment, which comprises the objects of cognition, among other things. So in that sense, objects and subjects are (as Buddhists say) 'co-arising'.

That sense is what 'embodied cognition' attempts to capture. And also the 'participatory realism' mentioned above. Both of those approaches sense that you can't really see 'the world' as if you're seeing it from no perspective; that is the sense in which I think they're both indebted to Kant.

I think the emphasis on 'objectivity' is very much a consequence of Enlightenment realism. By 'Enlightenment realism', I'm referring to the general notion that objective judgement holds sway over (for instance) religious conviction, that culture evolves towards a scientific outlook which is forever approaching a more and more complete or comprehensive understanding of reality.

The problem is, Enlightenment realism has forgotten it's buried premisses. It's grounded in an historically-conditioned perspective grounded in fundamental philosophical assumptions which nowadays are taken for granted as they so much condition the way our culture sees things. So seeing through those cultural tropes, can open up a more panoramic understanding of 'the nature of things' - not from a scientific or objectivist perspective, but through compassion. Because compassion is also unifying. Not in the sense of providing some 'grand synthesis' in an intellectual sense, but in providing a sense of kinship with others, and with life as a whole, that is normally one of the casualties of the 'objectivist' point of view.

I see this movement towards 'participatory realism' as signifying an actual cultural shift - a breaking down of that sense of 'otherness' which is intrinsic to the 'objectivist' understanding. It's part of the 'greening' of modern culture; the shift away from mechanist metaphors to bio-semiotics is another aspect of the same movement.

So - neither objective fact nor subjective opinion. Gradually a perspective is dawning which transcends both.

But that sense of an ordered unity is conspicuously absent from modern cosmology, what with the multiverses and parallel worlds and so on. — Wayfarer

I think modern cosmology still posits a unity in the sense of a unification of fundamental forces and laws. If there were parallel worlds or multiverses then they must have their own separate unities or else they would be unintelligible chaoses.

That sense is what 'embodied cognition' attempts to capture. And also the 'participatory realism' mentioned above. Both of those approaches sense that you can't really see 'the world' as if you're seeing it from no perspective; that is the sense in which I think they're both indebted to Kant. — Wayfarer

I would say that in one way or another everyone is indebted to Kant. The thing about participatory realism, which is really a kind of 'process' realism as opposed to an 'object' realism, is that there is still posited to be a mind independent "structure" (c.f. ontic structural realism) that is an ever-changing dynamic process and not a collection of determinate objects which are distinctly separate. It's more like a field of shifting differential intensities, which includes subjective experience as a unique kind of dynamis which is the most highly evolved. We are all participating in a world via the unique kind of self-organizing field intensities that we call "bodies".

The difference of this view from Kant is that the 'embodied' view says that the body provides the conditions of actual experience, and that the synthetic a priori forms of perception and categories of judgement are determined by the living body and not by a disembodied transcendental ego.

So, there is a universality to human experience and judgement, which is due to the fact that we are all embodied humans. But the commonalities cannot be precisely determined, which means that the only possibility for objectivity lies in intersubjectivity. It is always going to be a comparing of notes between subjects, and objective determinability lies along a continuum from the empirical to the metaphysical, from the most (but never absolute) determinability to the least (but never zero) determinability.