A recurring theme in discussions of late has been whether we can use the language of classical logic to make inferences about reality supposedly beyond the purview of empirical inquiry. This is the backbone of natural theology, as well as being subsumed under popular uses of the nebulous term 'metaphysics'. I've consistently maintained that this is a futile endeavor, and that intellectual fields like natural theology, or any 'metaphysical' proposition that assumes a priori truths to make inferences about reality, are fundamentally incoherent.
A helpful way to think about this is what physicists call a 'frame of reference'. We intuit reality in a classical, Newtonian frame of reference. The reason that quantum mechanics and Einstein's theories of relativity are counter-intuitive is because we don't live in black holes, we don't travel at the speed of light, and we don't live in a subatomic world. The 'laws' of classical logic, and the semantic and conceptual structure that comprises them, are abstracted from that everyday Newtonian frame of reference. So we should not be surprised when we examine other frames of reference and find the language of classical logic to fail us in providing a coherent description of these systems.
Let's take a phrase like 'beyond the universe'. The idea sounds provocative and intuitive because in our minds, we visualize the universe like a container; the stars, galaxies, space-time, people, and everything else we know is contained 'within' the universe. We can abstract the concept of an 'outside' of this container, and wonder what might exist and how it might behave. The problem is that the intuition is flawed; the very term 'beyond the universe' is incoherent. 'Beyond' denotes a spatiotemporal referent – that is what gives the word its meaning. But the universe is not a container, with space 'within' and 'beyond'; rather, space itself is a property of the universe. Spatiotemporal terminology like 'within' and 'beyond' simply cannot coherently describe the nature of the universe itself.
This is why the old theological conundrum "where did the universe come from?" is fundamentally a nonsensical question, like asking what is "before time", "South of the South Pole", or asking "what comes after eternity?" The concept of 'comes from' relies on those Newtonian intuitions about reality – cause and effect, beginning and end, within and beyond. Notice, for example, how William Lane Craig attempts to buttress his claim that "something cannot come from nothing" in his debate with Sean Carroll:
[Craig] said that if the universe began to exist there must be a transcendent cause; I said that everyday notions of causation don’t apply to the beginning of the universe and explained why they might apply approximately inside the universe but not to it; and his response was that if the universe could just pop into existence, why not bicycles?Bicycles can't pop into existence because they're composed of matter, are contained within space-time, and obey the physical laws of the universe. They exist within a specific frame of reference in which the governing laws are clearly defined according to a very specific semantic framework. But these things are, again, properties of the universe itself. The universe is not a discrete object like a bicycle to which the known laws of physics apply; the laws of physics are a property of the universe, so it's incoherent to make logical inferences about the universe itself the same way we'd make inferences about everyday physical objects. Our everyday metaphors are simply nonsensical in that frame of reference.
That's why the question of "Where did the universe come from?" is misguided; the universe cannot have 'come from' anything at all, including nothing. The universe simply is. Our semantics are simply ill-equipped to coherently describe it in any other way. The reason why phrases like 'beyond the universe', 'timeless existence', or 'non-physical cause' sound profound is precisely because their exact meaning is ambiguous. If I ask someone to specify what it means to say something is beyond the universe, I'll likely get an answer like "It means something not contained within the universe" – in which case they're relying the aforementioned fallacious metaphor.
Quantum mechanics and classical logic
I often bring up the example of quantum mechanics in these discussions, because I think it's helpful in understanding that there's another frame of reference, right here in the physical universe, in which the semantics of classical logic simply fail us. One cannot describe a quantum system using classical concepts like the law of identity or modus ponens. Does this mean that quantum mechanics contradicts classical logic? Not necessarily. The key to understanding why brings us back to frames of reference. At Newtonian scales, quantum irregularities 'smooth out' and the laws of logic are perfectly sensible and applicable. Just as we can't use Feynman's sum over histories to calculate the trajectory of a baseball in our everyday Newtonian frame of reference, we cannot use simple logical principles like modus ponens to calculate the trajectory of a particle in a quantum field.
Take quantum superposition as an example, in which a system (like a particle) exists in all possible states simultaneously. An experiment, described by New Scientist, clarifies the concept:
Does Schrödinger's cat really exist? You bet. The first ever quantum superposition in an object visible to the naked eye has been observed.
Aaron O'Connell and colleagues at the University of California, Santa Barbara, did not actually produce a cat that was dead and alive at the same time, as Erwin Schrödinger proposed in a notorious thought experiment 75 years ago. But they did show that a tiny resonating strip of metal – only 60 micrometres long, but big enough to be seen without a microscope – can both oscillate and not oscillate at the same time. Alas, you couldn't actually see the effect happening, because that very act of observation would take it out of superposition.Notice that the strip of metal could both oscillate and not oscillate simultaneously, apparently defying the laws of logic. But when the strip of metal is being observed directly, we must observe the strip of metal either oscillating or not. It's odd, and certainly counter-intuitive, but it highlights the fact that quantum systems do not lend themselves to the semantics of classical logic. Our direct observation, in our human/Newtonian frame of reference, however, does; that is because, contrary to what many armchair philosophers seem to assert, the 'laws' of logic are simply useful approximations of physical systems in a specific frame of reference – or, to put it another way, they are laws of human thought, not immutable laws of nature itself. Humans simply don't perceive or intuit reality in the framework of quantum systems.
I should clarify, though, that quantum mechanics – though I think it's a good example – is just an example. The argument that classical modal logic cannot be applied beyond the frame of reference from which its semantic structure is derived doesn't require the weirdness of quantum mechanics to be true – it's just a helpful example in clarifying the limitations of classical logic. The real challenge for theists, or 'metaphysicians' if they prefer a more pretentious moniker, is to clarify specific concepts:
- What is 'timeless existence' – that is, how can something exist without a past, present or future?
- How can a 'changeless mind', as Craig describes God, be functional – since function implies change?
- How can something exist immaterially? If it is not composed of nothing, then it is composed of something. But what is that something, and how can it exist in no place (or all places) or at no time (or all times)?
- What do things like 'non-physical time' or 'non-physical causality' mean? Since both time and causality describe processes of change, how can change or causality exist without a past, present, or future?
- How can something exist 'before' or 'beyond' the universe? Can such a thing be described without spatiotemporal metaphors?