DALL-E image of a circle of light with vague forms in a penumbra of darkness around it. http://schwitzsplinters.blogspot.com

"As the circle of light expands, so also does the ring of darkness around it" -- probably not Einstein

Within the ring of light lies what is straightforwardly knowable through common sense or mainstream science. Water is H2O. There's tea in this mug. Continents drift. You shouldn't schedule children's parties at 3:00 a.m. In the penumbra are matters of conjecture or speculation: There's alien life somewhere in the galaxy. Human beings are essentially just arrangements of material stuff. My retiring collegue will enjoy this Nietzsche finger puppet I bought for her.

Not all penumbral questions are philosophical, and philosophy doesn't dwell only in the penumbra. The question of whether there was once life on Mars is penumbral (not straightforwardly answerable), but it's not primarily philosophical, and neither is my question about the finger puppet -- at least not as these questions are normally approached. Also, some philosophical questions, for example about whether Kant ever wrote some particular sentence or whether Q follows from -P & (-Q -> P), lie well within the circle of light.

However, the penumbra is philosophy's familiar home; and any sufficiently broad question about the penumbra -- that is, concerning large, general issues that aren't straightforwardly answerable -- is worth regarding as a philosophical question. Some of these philosophical questions are addressed by big-picture speculative scientists, and some by philosophers. I draw no sharp distinction between them. If you're speculating about the most fundamental matters in any area, you're philosophizing, as far as I'm concerned.

I don't mean to suggest that things in the circle of light are known indubitably or exceptionlessly. I might be wrong about what's in my mug. A 3:00 a.m. party might be exactly what my group of jetlagged toddlers needs. Continental drift theory might someday be overturned. Maybe even radical skepticism is true and I'm just a brain in a vat, completely deluded about all such matters. Still, there's a distinction between what we reasonably regard as yielding to the ordinary methods of science and common sense and what we recognize as tending to elude such methods, requiring a more speculative approach. The latter is what occupies the penumbra. Of course, there's no sharp line between light and dark, nor a sharp beginning or end to the penumbra. Some penumbral questions -- what is the ultimate origin of the universe, if any, before the Big Bang -- lie with their far edge well into the darkness.

Nor is the penumbra fixed. As the initial quote suggests, the circle of light can grow. What was once penumbral -- whether humans and monkeys are genetically related, whether every true sentence of arithmetic is in principle provable -- can be illuminated. What was once wild philosophical speculation can become ordinary science.

The world is weird, as I argue in my recent book. Regarding fundamental questions of cosmology and consciousness, we are stuck with a variety of bizarre speculative possibilities, for none of which we have decisive evidence. What's the proper interpretation of the bizarreness of quantum mechanics? Could advanced AI systems have genuine conscious experiences? We don't know, and we can't for the foreseeable future find out. There's no straightforward way to settle these questions, and the deeper we probe, the more we lose ourselves in thickets of competing theoretical bizarreness.

Does that mean that we will never know whether the many worlds interpretation of quantum mechanics is correct or whether consciousness could arise in a sufficiently sophisticated silicon-based computer? This is one question my podcast interviewers often ask.  

No, that doesn't follow. Science can prove some pretty amazing things, given time. Who'd have thought a couple centuries ago that just by looking up at the stars we could learn so much strange detail about the early history of the universe?

But as the light grows, the penumbral ring will expand to match. There will always be darkness beyond. There will always be room for philosophical speculation. We will never complete the project of understanding the basic structure of world. If we figure out that X caused the Big Bang, we can then speculate about what caused X or whether X arose without a cause. If we figure out AI consciousness, in terms of Theory T of consciousness, we will uncover new topics of speculation concerning the wider applicability, or necessity, or fundamental grounds of Theory T.

Consider the Agrippan trilemma. To establish some proposition A, if we aren't just going to assume it without argument, we need an argument with at least one premise B. But then to establish proposition B, we need a further argument with at least one premise C. But then to establish C we need some further premise D, and so on. Either (1.) we simply stop dogmatically somewhere, assuming A (or B or C...) without argument; (2.) we argue in a circle, eventually coming back around to A (because B because C because D because... A); or (3.) we regress infinitely, so that there's always a new question to pursue, and we never reach an end.

The answer is that of course practically we need to start somewhere -- either with some premises we (perhaps reasonably) simply take for granted without further argument (Horn 1) or with some set of premises that mutually support each other and are assumed as a bundle (Horn 2). But we will always be able to ask why assume that proposition or bundle? We can always go deeper, more fundamental. We can always ask for the why behind the why behind the why. We can always wonder about the conditions of the possibility of the structure of the grounds of whatever it is that we currently regard as fundamental. Behind every curtain stands another curtain. There is no last curtain we can open after which we have a complete understanding.

This retreating-curtain view can be justified on Agrippan grounds. Or we can defend it by induction: Never so far have we found a once-penumbral question which, when answered, didn't reveal new, more fundamental questions behind it. Just try to find a counterexample! You won't, because whatever answer you give me, I can always respond with the toddler's trick of once again asking "why?"

Even within the light, it's of course entirely possible to be an annoying philosopher-toddler. My mug contains tea. Well, how do I know that? By looking in it. Well, how do I know that looking into a mug is a good way to learn about its contents? Well, um... now already I'm starting to do some philosophy. Maybe because looking in general has seemed to be a reliable process in the past. Well, how do I know that? And even if I do know it, how do I know that the past is a reliable guide to the future? Starting anywhere, we can quickly find layers of philosophical depth. Think of the circle of light, perhaps, not as a two-dimensional figure but instead as a thin disk in three-dimensional space. Even if you start at its middle, with the seemingly most straightforward and securely known facts, dig just a few questions deep and you will find penumbra and darkness.

Eric Schwitzgebel - http://schwitzsplinters.blogspot.com/2024/04/philosophy-and-ring-of-darkness.html