about all these things, memories that sprang into existence along with me and you five minutes ago, or a little longer ago, since you’ve been reading and thinking about it all for a bit now. But nothing existed before that cosmic appearance act roughly five minutes past. Weird. Bizarre. Crazy.
You might object right away, “But how do you know the Five-Minute Hypothesis is true?” If you react like this, your response is natural. The hypothesis admittedly sounds highly implausible, to the greatest possible degree. But that’s not the point. The skeptics who introduce such an idea don’t believe the Five-Minute Hypothesis to be true. And they are not trying to get you to believe it. They are just pointing out that the beliefs you now have commit you to firmly rejecting it as false, and they want to ask how in the world you know it, or even reasonably believe it, to be false.
On examination, it is easy to see that you can’t produce a single shred of good evidence that this ridiculous hypothesis is false. Anything you point to — hair on your head or anyone’s that has been around enough time to grow long, scars from wounds long ago, age circles in tree trunks, and so on — all of this is compatible with the hypothesis, which alleges that all these things, with their deceptive appearances of age, just sprang into existence within the past few minutes, as part of an elaborate cosmic trick.
But if you need some amount of good solid evidence in order to be rationally justified in believing anything, then you can’t rationally believe this radical hypothesis to be false. That wouldn’t mean that you had to believe it to be true. Not at all. It would just mean that you should withhold judgment on it, and become correspondingly uncertain about everything in the past, over five minutes ago. But that would mean giving up all the beliefs you have had concerning things actually having happened in the past. And that would be radical indeed.
Radical skepticism about the present
The thinker often referred to as the Father of Modern Philosophy, René Descartes (pronounced “Renay Day-Cart”) back in the 17th century offered his own radical suggestion. How do we know that the apparent objective life in the world we experience is not all an extraordinarily elaborate dream? The poet Robert Burns later picked up the idea with his own words, “Life and love are but a dream.” You could be dreaming that you are reading philosophy now. This skeptical reasoning you seem to be reading about could just be part of one big nightmare. Look at the room around you. Gaze down at your body and at what you’re wearing. How do you know that it’s not all just a dream? Modern filmmakers have taken up something like this idea with The Matrix franchise. Or maybe you just dreamed they did.
Descartes also toyed with the idea that present life could possibly all be one big delusion. Perhaps there is a very powerful evil demon who has hypnotized everyone, or just you, in case nobody else but you and the demon actually exist, deluding you to hold all these elaborate beliefs, and to seem to see and hear all the things they or you think are actually being experienced, moment to moment. You likely don’t for a second actually suspect that this might indeed be going on. But, again, why not? Philosopher Thomas Hobbes once referred to “The privilege of absurdity; to which no living creature is subject but man only.” And yes, it’s absurd. But the question is how we know it’s not also real.
The truth is, you cannot refute the Dream Hypothesis, or the Demon Hypothesis, or any such wild, comprehensive Matrix-type scenario. Do you then just live in a virtual, cosmic computer-type simulation? The surprising fact is that when you think about it hard enough, you come to realize that you can’t even come up with a single shred of positive, independent evidence that any of these radical scenarios is false. And yet everyone normally believes things that imply they are, in fact, false. This, the skeptic suggests, is a problem. You need some reason to think you’re right in having your ordinary beliefs, and denying these wild alternatives to be true, and yet you can’t seem to have any.
DESCARTES: REBEL WITHOUT A PAUSE
René Descartes, military man, mathematician, and philosophical whiz kid, was an ultimate intellectual rebel. As an experiment, he decided not to believe anything anyone had ever told him, and not even to trust his own senses. In an attempt to determine whether anything is utterly indubitable, or impossible to doubt, he proposed to try to doubt everything. One thing he concluded that he could not doubt or deny — the fact that in his very act of doubting, he was thinking. And from this, he saw it followed that he must actually exist. Thus he bequeathed to history the most famous piece of philosophical reasoning ever: “I think, therefore I am” (in French, “Je pense, donc je suis,” or in the more famous Latin formulation, “Cogito ergo sum.”). From this foundation, he then began to build up a body of knowledge he thought he could trust absolutely.
Radical skepticism about the future
It’s necessary to take at least the briefest of glances at beliefs about the future. The skeptic’s radical hypothesis here is one invented by a philosopher friend I often saved from the bumpers of oncoming cars in New Haven, Connecticut, years ago (when he wasn’t saving me, as we theorized our way down the sidewalks around Yale), contemporary philosopher and profound thinker J.L.A. Garcia. It’s called Futuristic Nihilism and is very simple.
The futuristic nihilist points out that the future does not exist. Yet. But there is a problem. In order for a belief to be true, the object about which it is true must be among the furniture of reality, the sum total of things that exist, and that object must have the property attributed to it in that belief. For it to be true that grass is green, there must be such a thing as grass, and it must have the property of being green. But the future is right now just one huge void. You may pour into that void lots of beliefs about what will happen later today, what will transpire tomorrow, and what will occur later this year. You likely hold beliefs about the next decade. You may be deep into many beliefs about the future, however tentative and cautious you might try to be with this territory. But the future does not yet exist to have any qualities or ground any truths. And that applies to the very near future, including beliefs you have about stuff an hour from now, or tomorrow. Those times don’t yet exist.
The future-oriented radical skeptic could buttress his argument even further by plugging in to some of the other forms of radical skepticism. Think about the radical hypotheses of the previous section. At any second, you could wake up from Descartes’ Dream and find things in the immediate future to be very different from what you might have inductively inferred, based on a delusory past. Or Descartes’ Demon could snap his fingers and wake you up to an extremely divergent present and future from anything you expect. The deception could change radically. How do you know any of this won’t happen any minute now and pull the rug out from under your future-oriented beliefs? To this question there is no good answer. And that’s really very odd. You may get to this point in our journey and understand in a new way the poet Coleridge’s words when he wrote: “My mind is in a state of philosophical doubt.” And, yeah: Ouch.
What the skeptics show us
The questions of source skepticism showed that you can’t come up with any good evidence that your most basic belief-forming mechanisms are ever reliable. The questions of radical skepticism then poured salt on the wound, pointing out that you can’t find any single shred of evidence at all to refute or even dislodge an array of crazy-sounding radical hypotheses that are logically incompatible with your current beliefs about vitally important things.
When it’s good to doubt your doubts