The fact that you can derive an ‘ought’ from an ‘is’ is manifestly wrong, just logically wrong. Facts in — facts out, values in — values out. By rules of deductive logic you can’t derive conclusions about properties that did not initially appear in your premises. Deriving an ‘ought’ from an ‘is’ is like adding two even numbers and obtaining an odd one. There is no description of the universe which contains oughts, descriptions of the universe only contain facts. So oughts stay on the one side, facts stay on the other. Right? Well, not so fast.
Even on Hume’s own terms, you can’t derive an ought from an is without making further assumptions. If you make further assumptions, you can derive as many oughts as you please. So, for example, you may find it reasonable to assume that you should avoid unnecessary pain. Granted this, you can then logically derive that you ought not stick your hands in boiling water without having a good reason for doing so.
The thing about humans is that we share a lot of common assumptions about what we should and should not do. After all, we are all members of the same species sharing very similar biology and minds. Your strivings and thinkings may in many ways be different to mine, but they are much closer to each other than they are to a chimp’s. It is safe to say that we all want to suffer less and enjoy our lives more. None of us like putting our hands in boiling water and none of us wear shoes two sizes smaller than our feet. We all strive for love, acceptance and fulfilment. We find ourselves on a shared planet in a shared condition. Which means we all share some important assumptions about what we ought to do. And this means that in everyday circumstance it is often perfectly fine to jump from an is to an ought.
Now, philosophers reading this have probably winced. What I often hear goes something like this “Well, you can’t logically prove that we have similar assumptions. Really, I may have totally different assumptions from you and you have no way of proving that I don’t.” The problem with some philosophers is that they don’t put their money where their mouth is. What I always propose in response to the above statement is this — If we really don’t have any assumptions in common, then why don’t you go and stick your hand into a pot of boiling water? Haven’t seen any steaming red hands yet.
The whole emphasis on logical deduction seems questionable. There are very few things in our lives that we can logically deduce and yet somehow life still works. We can’t logically deduce laws of gravity, yet rockets fly into space. We can’t logically deduce that terrible spaghetti monster does not exist, yet we don’t worry about him too much. Some people even take Hume’s remark to mean that there can’t be any moral knowledge. Moral relativism follows. And this is a grave mistake.
Imagine that you learn the theory of relativity in your physics class. There you are told that there are no absolute velocities, that velocities are always relative. In outer space there really isn’t any way to answer the question “How fast am I going?” In fact, the question itself makes no sense — you have to be going relative to something. Armed with this knowledge you attack highway 101 doing 60 miles over the limit. And when you get pulled over you say “Officer, what do you mean I was going 120 miles per hour? There are no absolute velocities, you should know that!” Exactly this messed up logic is often used to justify terrible atrocities. For example, there are people out there who actually believe that mutilating female genitalia is ok as long as it is an accepted cultural norm.
Just as there are no absolute velocities, there are no absolute moral laws out there, hanging in space, waiting to be discovered. But there are better, worse and plain wrong answers to moral questions here on Earth, among human beings. These answers will probably not work for someone on Alpha Centauri. Heck, the answers will probably change even for us as we evolve. Or degrade. Either way, we can’t logically derive those answers. And we don’t need to. Just like in science, we are not really after a derivation — we are after an explanation.
The deeper problem with Hume’s argument has to do with how we use language. He takes it for granted that there are such things as ‘facts’ and ‘values’ and that they occupy different pools of logical properties that don’t intermingle. But in doing so, Hume takes language to be some sort of a logical derivation engine. Which it is not. Wittgenstein made that mistake when he wrote Tractatus. He then thought about the matter a little further and realized he was wrong. In his Philosophical Investigations he imagines language to be a kind of game, following different rules in different scenarios, and sometimes — hardly any rules at all. We don’t come to know different words through their definitions, we come to know them through their use.
To make this concrete, let’s take chickens and eggs and ask the notorious question “What came first?” — but with a catch. We have to imagine ourselves in a time before genetics, before Darwin, before evolutionary biology. Back then the concept of an egg had certain rather limited properties. Three dominant ones where:
a) It is laid by a chicken,
b) It is good for food and,
c) If it is not used for food, chicken comes out of it.
And similarly for chickens. Given this impoverished understanding of what an egg is and what a chicken is, the question “What came first?” becomes strangely loopy and people start arriving at some very peculiar conclusions. As per Wikipedia:
Aristotle, writing in the fourth century BCE, concluded that this was an infinite sequence, with no true origin. Plutarch, writing four centuries later, specifically highlighted this question as bearing on a “great and weighty problem (whether the world had a beginning).” By the end of the 16th century, the well-known question seemed to have been regarded as settled in the Christian world, based on the origin story of the Bible. In describing the creation of animals, it allows for a first chicken that did not come from an egg.
The problem was of course not with chickens or eggs, but with our knowledge and language. We were playing a certain language game with our limited conceptions and we thought that it somehow enlightened us about the mysteries of the universe. But in reality it was just that — a language game. As our understanding of life progressed, new properties got added, such as
c) Chickens are a part of an interconnected web of life, sharing common ancestor with every other living creature on the planet and
d) Chickens are made of trillions of cells each one containing mind-blowing molecular machinery that allows them to replicate and evolve.
These new additions drastically changed our understanding of domesticated fowls and finally allowed us to answer the “What came first?” question properly.
I have a feeling that in insisting that facts and values belong to different property domains, we are once again taking language too seriously. We are playing chicken and egg game without evolutionary biology. This is like wrapping our minds around Zeno’s paradox without calculus. We have certain limited conception of what a fact is and what a value is, and from that we make some doubtful conclusions. But what is a fact, really? What is a value, really? I don’t think we have sufficiently good answers to these questions. What we do know, is that facts and values are not as independent as Hume likes to put it. After all, a value is a product of human thinking. Thinking is a product of brain activity. And brain activity is a factual matter contingent on physics, chemistry, and evolutionary history among other things. So at least in part values stem from physical stuff. Which is not surprising — where are they supposed to come from but from what actually exists? In other words, from what is.