My argument is not that the world doesn't exist in the absence of any or all observers, but that whatever we can say we know about what exists, presupposes a perspective. Even if that is mathematicized, which effectively eliminates purely individual perspectives and gives a kind of 'weighted average' of all points of view, it's still an irreducibly human point of view, which is inextricably an aspect of whatever we say exists. — Wayfarer
I agree. Your view contrasts with the view expressed by Sean Carroll (quoted) in the OP of this thread. Physicists often are happy to equate "the Universe" -- the totality of what exists -- with some comprehensive set of "initial conditions" conjoined with a set of universally quantified statements ("universal laws"). Everything (i.e. every empirical truth; every state of affairs) is supposed to be determined by the initial conditions and the laws. This is a view of the "block universe" in which time just is another dimension akin to the three spatial dimensions. The human perception of the flow of time is alleged to be an illusion stemming from of our merely subjective perspective, not just in point of temporal scale, as mentioned by Wayfarer, but also regarding the distinctions between present, past and future, which are taken not to be of any relevance to the objectively existing fabric of the world. Hence, Sean Carroll is led to downgrade the objectivity of the very notion of causality. In his view, nothing ever really comes into existence. The "block universe" being "eternal" at a fundamental level, events (or states of affairs) need not be caused to occur (or to be as they are) since the laws of physics govern everything and the way in which they govern consists in them fully constraining the mathematical relationships between the layout of the universe at all the singular moments of time (i.e. in between elements of a full set of space-like slices of the eternally existing "block universe").
Such a view of the universe can't of course mesh with our view of the world as a source of possible objects of experience. Kant argues in the
Analogies of Experience (in his CPR) that an empirical experience can't have an objective purport if it doesn't potentially rationally bear on other experiences. (Wilfrid Sellars also argued for this in his
Empiricism and the Philosophy of Mind currently being discussed in another thread). And this is only possible if we can distinguish the
successive experiences of a
single thing that has changed from the
simultaneous experiences of
two separately existing things. The possibility of our conceiving of this simultaneity/succession distinction, in turn, depends on our ability to recognize laws that govern the evolution of enduring substances (i.e. laws that state their persistence conditions and their fallible (active and passive) powers. (Why those powers must be fallible is explained by Sebastian Rödl in his book
Categories of the Temporal). If it were conceivable that any "substance" could be experienced to have become any other "substance", with no law governing how its qualities tend to change over time, then there would be no telling if two qualitatively distinct experiences refer to the same object (at different times) or to two distinct objects (at the same time). Thus, the possibility of the objectivity of experience presupposes the possibility of the experience of time (as a formal condition, rather than as a material content) and the possibility of the experience of time, in turn, presupposes the ability to recognize substances governed by laws. So, in sum, the category of a substance -- of an enduring object that can be experienced at different moments of time and that is governed by laws that specify its powers -- must be brought to bear by an experiencing subject to all her experiences if they are to have objective purport at all. If this is right, the formal concepts of substance and of time are prerequisites of the intelligibility of the world.
But, can't the world be simply conceived to exist (i.e. be intelligibly be judged to exist) without its satisfying the condition of its also being a potential object of experience by agents possessed of finite intellects like us? This was the issue being discussed by Agustino, John and Michael regarding the existence of the Earth before there were humans experiencing it. It is important to recognize that the Earth is a potential object of experience of a distinctive formal kind. It is an enduring substance. As such, it doesn't exist qua object of experience independently of the specific substance concept that it is taken to falls under -- e.g. the concept of a rocky planet -- which specifies its conditions of persistence and individuation. Those conditions are tied up with the concept and aren't independent of our interests in individuating it thus. If we wonder at what point in time the Earth began to exist, for instance, this question can't be made sense of quite independently of our criteria for an object's inclusion into the (substance) category of a rocky planet. So, this is why the claim that the Earth existed before there were humans quite independently of whatever humans ever thought regarding what it is that makes a planet the sort of thing that it is doesn't quite make sense. The existence of the Earth, qua
possible object of experience, doesn't depend on there actually existing humans actually or potentially experiencing it, which is something Agustino would be correct about if it were his only claim. But the very sense and intelligibility of the state of affairs being considered -- e.g. that the Earth existed three billion years ago -- is relative to some substance concept or other that corresponds to the specific interests of a potential subject of experience.
Sean Carroll's block universe, as he conceives it, within which time just is an objective parameter, doesn't contain any planet because this conception lack any criterion according to which some set of "particles" does or does no make up a "planet" in any specific space-like slice of his "objective" (so called) universe.