I couldn’t wait for Roger Waters’s tour, Pros and Cons of Hitchhiking. I got a shirt and the vinyl (which I still have). But this article isn’t just a case of nostalgia: It’s a philosophical question about reality and fantasy.

The “plot” of Pros and Cons, if that makes any sense, is a series of seemingly random thoughts of a man driving through California, including a fantasy about sex with a hitchhiker he picks up during his trip (and maybe the hitchhiker, too).  The lyrics are fascinating, as they intersperse realities of his life (and perhaps, as some people think, his mid-life crisis) with his fantasies. The trick, of course, is to tell which is which.

And that trick brings us to what-if-ery. Oddly enough, what-if-ery appears in what we easily recognize as ordinary problem-solving: What if I pick up the dry cleaning before going shopping for groceries, since it’s on the way?

I will take it as a presumption that what-if in problem solving is legitimate, but when does it go too far? When is what-if illegitimate in our thinking?

Let’s start with some help from Kant. What-if-ery is legitimate when applied to what is experienceable by us. (I realize that there’s a lot packed into this interpretation of Kant, but I won’t unpack here. If you’d like a dose of Kant, let me know, and I’ll see what I can do.) When a particular what-if is applied beyond the reach of experience, there’s trouble.

Suppose I am obviously in distress, and you ask me what’s wrong. I explain that I’m deeply conflicted. “What if I had gone into medicine instead of philosophy? Maybe I made the wrong choice.” Certainly, we can empathize: I imagine we have all had moments in which we reflect on our choices and experience this conflict. But suppose I continue: “So, from today, my life goal is to have chosen medicine instead of philosophy.”

The obvious difficulty with my life’s goal is that it is beyond the reach of the experienceable. I can’t strive for something that involves changing a historical “given.” It is a brute fact that I made the choices I made in the past. Period. (That’s a period with a lot of philosophical baggage — which I will also put aside for the moment.)

My “goal” may well have arisen from a line of thought that starts with a particular what-if: What if I had become a physician? Undoubtedly, I would have had a different life in many respects, but my line of thought in filling in those consequences is based on an event, a choice, that is beyond the reach of experience: I can imagine, but I cannot experience what it would be like to have chose medicine. This means, strictly speaking, that I cannot get myself in a position to establish whether my claims are correct (or incorrect). If such claims cannot be known to be correct or incorrect, then one may well wonder how they could serve to ground or guide us.

And now we come to the gist of the philosophical problem inspired by Pros and Cons: What bits of what-if-ery should we take seriously, if we want to be grounded? And in fact, what does it mean to be grounded?

Turning to the practical business of managing one’s life, if the what-if path through zones beyond experience leads to claims that no one can take seriously as grounding or guiding in our choices, then why spend time entertaining them? Note that “no one” in the previous sentence is a universal quantifier: It includes the proposer of this what-if, as well as the rest of us. How can I take myself seriously if I strive toward having chosen medicine?

Here’s where this exploration gets interesting. When the goal is so blatantly contrary to fact, we don’t have a lot of empathy. But how do we react when the what-if-ery is emotionally compelling?

Consider a different what-if: What if I had pursued the relationship with John instead of James? This what-if seems to make more sense — but why? This past choice is just as much beyond reach as the moment I chose philosophy over medicine.

Perhaps reflection on this notion of the reach of experience can free us from the grip of what-if-ery that is merely emotionally compelling, but not rationally grounding.

I am not arguing that emotion is unimportant. Indeed, it is one of Nature’s great gifts. What I am saying is that emotional motivations need not be epistemic trump-cards.

William James, in Varieties of Religious Experience, divides people into two fundamental types: Error-avoiders and Truth-seekers. Error-avoiders take few epistemic risks, but they may take a larger risk of missing truths that require going out on a limb. Truth-seekers are willing to risk in the pursuit of truth, but they also risk losing the ground for their beliefs.

Error-avoiders are entitled to their caution, just as Truth-seekers are entitled to their epistemic exuberance. What neither Error-avoiders nor Truth-seekers are entitled to is believing what is demonstrably false. And so, it seems, they need each other, to find grounded guidance.

Sometimes, when I talk like this in public, people accuse me of holding a “pessimistic” view that leaves no room for hope. I don’t agree that it is pessimistic to look for grounded guidance in the pursuit of a life of flourishing — but I willingly accept the charge that I don’t leave much room for hope. But let’s leave that discussion is for another day.