According to many, philosophy is primarily an armchair discipline. Philosophical work is carried out mainly at the level of logic and concepts. Just like math puzzles, chess puzzles, logic puzzles, crossword puzzles and sudoku puzzles, if philosophical puzzles can be solved at all, then they can be solved in the head. We don’t need to observe the world to solve them. We need only sit in our favourite armchair, close our eyes, insert our earplugs, and think.

I think this characterisation of philosophy as an armchair discipline is broadly correct. But I also lean towards what’s known as empiricism: the view that if you want to discover anything about how things stand outside your own mind, then you need to rely on observation. Our senses, say the empiricists, provide our only window on to external reality.

Why embrace empiricism? One popular reason is that it’s difficult to see how we could be sensitive to how things stand in our own minds reality other than by means of our senses. For how else could we be sensitive to the world “out there”? If there are external, mind-independent facts to be discovered, surely we’ll need to observe the world in order to reveal them. Sitting in our armchairs and having a good think will get us nowhere.

But then here is a dilemma for philosophers: if philosophy is an armchair discipline, and yet we can discover nothing about the world out there just by sitting in our armchairs and thinking, then philosophy is incapable revealing anything about that world.

Yet isn’t that a key job of philosophy: to reveal how reality fundamentally is? 

So, if empiricism is true, and I suspect it is, then it might seem that philosophy can’t do what many want it to do. Philosophy will be a grand waste of time so far as revealing how reality actually is.

This, I suspect, is why quite a few scientists disparage philosophy: it’s why physicist Stephen Hawking pronounced “philosophy is dead” and chemist Prof Peter Atkins condemns philosophy as “a complete waste of time.” If you want to know how the world out there really is, then you need to do science, not waste your time with philosophy. So far as that sort of inquiry is concerned, philosophy can amount to nothing beyond self-indulgent navel-gazing.

Now I lean towards empiricism, yet I’m a philosopher who thinks philosophy is a valuable discipline. So how do I go about resolving this dilemma that empiricism seems to make philosophy a grand waste of time?

I accept that if you want to discover how things stand in external reality, then philosophy is a grand waste of time. However, I just don’t think that’s what philosophy aims to do – or should aim to do. Perhaps some philosophers think that, from the comfort of their armchairs they can penetrate the veil and discern the fundamental nature of reality, but on my view, they’ll get nowhere. If you want to know how external reality is, you need to observe it. In fact, you’ll often need to do observation-based science. 

So, I have a relatively modest conception of what philosophy is capable of. I don’t think it can do what some philosophers think it can do. Yet, I’ll argue, that still leaves a great deal of important work for philosophy.  But what sort of work? Below I outline one important thing philosophy can do.

Conceptual puzzles

Philosophical puzzles often have the character of conceptual puzzles, and conceptual puzzles require armchair solutions. Take for example, this simple non-philosophical conceptual puzzle. At a family gathering, the following relations hold between those present: Son, Daughter, Mother, Father, Aunt, Uncle, Niece, Nephew, and Cousin. The question is: could there have been just four people present at that gathering?

At first sight, the answer might seem obvious: no. Surely there would have to be more than just four people present to get all those different connections holding between them. However, appearances are deceptive. A little armchair reflection can reveal that all these connections can exist between just four people (e.g. a brother and sister with a daughter and son, respectively) This is an interesting result: what seemed to be ruled out conceptually turns out, on closer examination, not to be ruled out after all. And his is a discovery we just made from our armchairs.

So we can, from the comfort of our armchairs, make surprising discoveries about what’s possible. Another thing we can do from the comfort of our armchairs is reveal that what seemed possible is actually logically or conceptually ruled out. Galileo famously did just this with the following thought experiment.

Galileo’s thought experiment

Aristotle’s theory of motion predicts that a heavier object will fall faster than a lighter object. At first sight, it seems that Aristotle’s theory might be true. In order to test it, we could take a heavier and lighter ball and drop them off the top a tower to see if the heavier lands first. However, Galileo didn’t need to do that. He refuted Aristotle’s theory from the comfort of his armchair, by performing a thought experiment. Galileo asks us to imagine that we take our two balls and link them with a chain. Aristotle’s theory predicts that the lighter ball will fall more slowly, and so should move behind the heavier ball, until the chain comes tight, at which point it will start to function as a brake, resulting in the two connected balls falling more slowly than would the heavier ball on its own. However, Aristotle’s theory also predicts that as we have now combined the two balls with the chain, the result is an even heavier object, and so the two balls combined should fall faster than did the solo heavier ball. But then Aristotle’s theory generates a logical contradiction: the connected balls both will and will not, fall faster than did the solo heavier ball. As Aristotle’s generates contradictions, it cannot be true. Galileo refuted Aristotle’s theory from the comfort of his armchair, just by having a think.

So a mere thought experiment involving imaginary objects can sometimes be as effective in ruling out a theory as a real experiment involving real objects. 

However, notice that neither of our two armchair investigations reveals how external reality actually is. What an armchair investigation cannot do is reveal what our two connected balls will actually do when released. They may fall faster than the single heavy ball, or more slowly, or they may turn into doves and fly off in the sunset. We can’t know without observation. All that our armchair investigations have done is establish what’s logically or conceptually possible and what’s not. 

So armchair investigations and thought experiments can reveal important truths. They can even refute scientific theories (by revealing logical or conceptual inconsistencies within them). But, because I lean towards empiricism, I don’t think they can reveal how external reality actually is.

So far we have been looking at some non-philosophical examples of how armchair investigation can reveal important and surprising truths. Let’s now turn to philosophy.

The mind-body problem as a philosophical problem

Philosophical puzzles are often conceptual puzzles. Take the mind-body problem. Some people think that no material object could ever be conscious. The believe the conscious mind must be something distinct – something immaterial.

What motivates this conclusion is often a little armchair reflection. The immaterialist thinks: ‘My technicolour, private internal landscape of thoughts, feelings and sensations, of which I have direct awareness as a conscious subject, just couldn’t be material. I can know, by reflecting a little on my own private subject experience, that this is just not the sort of thing that mere material object could have. To suppose you could build a consciousness out of unconscious material components is like supposing you could, say, build Beethoven’s Ninth Symphony out of Lego bricks. We can know, just by thinking about it, that it cannot be done. Mind and body are categorically different sorts of thing.

Of course, it’s one thing to point out the private introspected mind doesn’t seem, introspectively, to be the sort of thing that a material object could have, and another to provide an argument for that conclusion. Many philosophers have attempted to provide such an armchair argument, including, for example, Rene Descartes.

Famously, Descartes is widely supposed to have argued from his armchair like so:

I can doubt that my body exists 

I cannot doubt that I exist

Therefore: I am not my body

Descartes supports the first premise by supposing that he may be the subject of an illusion conjured up by an Evil Demon who is feeding his mind deceptive appearances, including the appearance that he has a body. Descartes supports his second premise by pointing out that, by doubting he exists, he demonstrates he exists, so it’s a self-defeating doubt.

While the premises of Descartes’ argument may be true, his argument fails. To see why it must fail, consider an analogy. Suppose I enter a hall of mirrors. I see someone over there in a mirror. I don’t think that it’s me (I suspect it’s someone else, or a mannequin, or perhaps even a computer generated illusion). I then attempt to prove it’s not me like so:

I can doubt that that person exists 

I cannot doubt that I exist

Therefore: I am not that person

Clearly that could still be me in the mirror. So there’s something wrong with this argument, logically speaking. Yet Descartes’ argument has the exact same logical form. So Descartes’ argument must share the same logical flaw. Descartes’ analogous argument must similarly fail.

Of course, there are others – materialists – who insist minds are brains and that it is possible to build a conscious mind out of non-conscious material components. They insist that what might seem like a conceptual obstacle to minds being brains is merely an apparent obstacle. Just as we figured out that, while there seemed to be a conceptual obstacle to there being just four people at that family gathering, that obstacle was illusory, so we can figure out that this obstacle is illusory too. 

The one way in which you won’t solve the conceptual puzzle of how mind can be brain is by doing observational science. Someone who thinks science is the appropriate arbiter here has misunderstood the puzzle. The philosophical problem of consciousness is a conceptual puzzle, just like our puzzle about the family gathering. Solving it requires working at the level of concepts.

Of course, once we’ve shown, in principle, that minds can be brains, it’s then a scientific, technical matter to show exactly how you go about creating consciousness by combining non-conscious physical components in the right way.

Scientists can and have revealed correlations between what happens physically in our brains and what happens in our conscious minds. But establishing things are correlated does not establish they are identical. Smoke and fire are correlated, but they’re not identical. Simply asserting, as the scientist Susan Greenfield does in her BBC series Brain Story, that “you are your brain” just presupposes a way out of the problem. If you actually want to solve that puzzle, then you’ll need to do armchair conceptual work, not science.

In this essay, I have provided some examples of the kind of puzzles philosophers work on, and why armchair methods are appropriate. Yes, philosophy may be useless at revealing how things stand in the world “out there.” For that, you’ll need observation. But that doesn’t mean that, as Stephen Hawking remarks, philosophy is dead, or, as Peter Atkins puts it, a complete waste of time. There’s still plenty of important work for philosophy to do, of which I have provided an example.

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Stephen Law is Director of the CertHE and Director of Studies in Philosophy, Oxford University Department of Continuing Education, and author of popular philosophy books including The Philosophy Gym: 25 short adventures in thinking.