On the Schopenhauer discussion (ep #114), I referred to his view qua idealist that, really, there was no world per se before the first perceiver, but also that science is correct in investigating ancient history, i.e. the world before perceivers. How could both of these claims be true? This is a general problem that idealism must address, summed up adequately by the old chestnut about the tree falling in the forest: The idealist must say that no, it doesn't make a sound, and in fact there's no tree or falling at all unless something (not necessarily a person) is there to witness it, to be a subject and thereby create it as a distinct object. Yet science still needs to work, i.e. people should be able to come along later and truly say that yes, there was a tree here standing, and it fell at such and such a time from such and such causes.
Here's Schopenhauer's formulation, from book I, section 7, original text pages 37-40. The context is the philosophy of science, and the difficulties that a purely mechanistic conception (which I think is the kind that at least we non-scientists generally think of as essential to science today), and he also bashes the idea early here of reductionism in science, which would entail that metaphysically, one should be able to reduce everything going on at a psychological level to biology, biology to chemistry, and chemistry to physics (which I also think is a guiding assumption of natural science, but Wes was arguing that non-reductionism is admitted by most philosophers of science; certainly one can't translate the vocabulary of biology into the vocabulary of physics). The bolding of key statements below is mine, as are some of the paragraph breaks:
We cannot understand how... one state could ever experience a chemical change, if there did not exist a second state to affect it. Thus the same difficulty appears in chemistry which Epicurus met with in mechanics. For he had to show how the first atom departed from the original direction of its motion. Indeed this contradiction, which... can neither be escaped nor solved, might quite properly be set up as a chemical antinomy...
...We see ever more clearly that what is chemical can never be referred to what is mechanical, nor what is organic to what is chemical or electrical. Those who in our own day are entering anew on this old, misleading path, will soon slink back silent and ashamed, as all their predecessors have done before them... Materialism... even at its birth, has death in its heart, because it ignores the subject and the forms of knowledge, which are presupposed, just as much in the case of the crudest matter, from which it desires to start, as in that of the organism, at which it desires to arrive. For, “no object without a subject,” is the principle which renders all materialism for ever impossible. Suns and planets without an eye that sees them, and an understanding that knows them, may indeed be spoken of in words, but for the idea, these words are absolutely meaningless.
On the other hand, the law of causality and the treatment and investigation of nature which is based upon it, lead us necessarily to the conclusion that, in time, each more highly organised state of matter has succeeded a cruder state: so that the lower animals existed before men, fishes before land animals, plants before fishes, and the unorganised before all that is organised; that, consequently, the original mass had to pass through a long series of changes before the first eye could be opened. And yet, the existence of this whole world remains ever dependent upon the first eye that opened, even if it were that of an insect. For such an eye is a necessary condition of the possibility of knowledge, and the whole world exists only in and for knowledge, and without it is not even thinkable. The world is entirely idea, and as such demands the knowing subject as the supporter of its existence. This long course of time itself, filled with innumerable changes, through which matter rose from form to form till at last the first percipient creature appeared,—this whole time itself is only thinkable in the identity of a consciousness whose succession of ideas, whose form of knowing it is, and apart from which, it loses all meaning and is nothing at all.
Thus we see, on the one hand, the existence of the whole world necessarily dependent upon the first conscious being, however undeveloped it may be; on the other hand, this conscious being just as necessarily entirely dependent upon a long chain of causes and effects which have preceded it, and in which it itself appears as a small link. These two contradictory points of view, to each of which we are led with the same necessity, we might again call an antinomy in our faculty of knowledge... The necessary contradiction which at last presents itself to us here, finds its solution in the fact that, to use Kant's phraseology, time, space, and causality do not belong to the thing-in-itself, but only to its phenomena, of which they are the form; which in my language means this: The objective world, the world as idea, is not the only side of the world, but merely its outward side; and it has an entirely different side—the side of its inmost nature—its kernel—the thing-in-itself... But the world as idea... only appears with the opening of the first eye. Without this medium of knowledge it cannot be, and therefore it was not before it. But without that eye, that is to say, outside of knowledge, there was also no before, no time. Thus time has no beginning, but all beginning is in time.
Since, however, it is the most universal form of the knowable, in which all phenomena are united together through causality, time, with its infinity of past and future, is present in the beginning of knowledge. The phenomenon which fills the first present must at once be known as causally bound up with and dependent upon a sequence of phenomena which stretches infinitely into the past, and this past itself is just as truly conditioned by this first present, as conversely the present is by the past. Accordingly the past out of which the first present arises, is, like it, dependent upon the knowing subject, without which it is nothing. It necessarily happens, however, that this first present does not manifest itself as the first, that is, as having no past for its parent, but as being the beginning of time. It manifests itself rather as the consequence of the past, according to the principle of existence in time. In the same way, the phenomena which fill this first present appear as the effects of earlier phenomena which filled the past, in accordance with the law of causality. Those who like mythological interpretations may take the birth of Kronos, the youngest of the Titans, as a symbol of the moment here referred to at which time appears, though, indeed it has no beginning; for with him, since he ate his father, the crude productions of heaven and earth cease, and the races of gods and men appear upon the scene.
You may recall that for Kant, whether or not time has a beginning or not is an antinomy: There are equally good reasons on both sides, and so the correct answer it to say that we just can't know and/or that the question somehow doesn't make sense. Temporal sequence only applies to phenomena, which depend on minds, so asking whether things in themselves are in an infinite or finite temporal series is attempting to use the concept of time outside of the realm in which it was developed, which is the realm of our experience. It does not follow from this that the Thing-In-Itself is atemporal, but simply that the Thing-In-Itself is not something we're in any position to make a judgment either way about. Compare to the question "Is God green?" You might say qua Maimonides that no, of course God is not green; colors apply to finite things. But neither can we positively say that God has the positive property of not being green, or not having color. Maybe He does have color, but in some higher way that we can't understand. We are in the same position regarding the Thing-In-Itself: by definition it's something we can't perceive or even really conceive of in its wholeness, in its essence, in its positive aspects.
Schopenhauer thinks that Kant is in no position to decide this issue "by definition," and thinks he has other reasons (mystical and artistic experience, i.e. the verdict of genius, plus the philosophy of science considerations surrounding "force" belabored in our discussion) for thinking we can know some positive things about the Thing-In-Itself, but he still fundamentally doesn't give us a reason for insisting on its lack of plurality and hence its non-temporal, non-spatial status. So why does he insist on this? I think he's just adhering to the heuristic (Kant might call it a regulative principle of Reason) to seek simplicity/unity. Saying that ultimately existence is One is supposed to be more satisfying somehow than saying that it's irreducibly Many. It's somewhat ironic that Schopenhauer dismisses this principle when it comes to science (in his rejection of reductionism) only to assert such unity at the metaphysical level.
Setting that aside, and granting Schopenhauer the point about the Thing-In-Itself's unified, atemporal character, and granting him the (contentious) proposition that differentiation within the Thing-In-Itself (the Will) only happens because perceivers pop up to perceive some part of the Will, haven't we just pushed the antinomy back one level? Schopenhauer is able to answer the question "does time have a beginning of not" by saying "no, not on the level of representation, but yes, before the first perceiver, there was no time," but he is then faced with a similarly insoluble question: "How could the first perceiver perceive something unless there was something already there to perceive?" This is to ask "why the principium individuationis?" which is in Schopenhauer's system the tragic question of Being.