Other writings     Drawings gallery

Braaaains on a Plane

Are there any good arguments for believing in other minds? Justify your answer.


I shall argue against single-mind solipsism and in extension the zombie hypothesis by inference to the best explanation.

Limitations of the Problem

Image by courtesy of A Tribe Called Möw.

Image by courtesy of A Tribe Called Möw.

The presupposition of the problem is that each person can only ever have direct experience of his or her own mind. Therefore, in lieu of any evidence to the contrary there is no reason to assume that any mind other than one’s own exists. I posit that there are only two ways that this could be the case. Either we must grant veracity to the zombie hypothesis or alternately to the notion of the outside world as a mirage, a dream, or something similarly illusory.

In this essay I shall take a non-illusory outside world for granted. Therefore, I will focus solely on it either being the case that other people do have minds or that they are zombies. I readily grant that an argument against realism would undermine my stance but it would fall outside the scope of this essay. It could be the case that only some people have minds, but since this also requires the existence of zombies I shall treat it as interchangeable with the idea that only one’s own mind exists.

I shall also take the word ‘mind’ more or less for granted. It is conceivable that no two minds are ever even remotely alike and that the word therefore is close to meaningless. However, to allude to Wittgenstein’s famous ‘Beetle in the Box’ analogy (Philosophical Investigations, 1958, §293) it is sufficient for the purpose of my argument that we should see ‘the box’ as containing something as opposed to being entirely void of content. That is, I am not concerned with what precisely – if anything – we mean by the word but just that there is some sort of subjective experience of qualia or internal conscious states present in other people as opposed to none at all.

The Zombie Hypothesis

By ‘the Zombie Hypothesis’ I merely refer to the notion that there are – or could be – entities that are ‘exactly like [me] in all physical respects but have no conscious experiences (Kirk, 2008).’ In this context I am arguing against, single-mind solipsism, by which I mean that one’s own mind is – or could be – the sole mind in existence. Full-blown metaphysical solipsism – wherein the existence of even a reality outside one’s own mind in general is brought into question – is another matter.

We are prone to argue by analogy that we can clearly see other people exhibit behaviour and presumable agency, which in our own case necessitates antecedent mental states. We therefore conclude that they, like us, must possess such mental states. The strongest objection against this is that we are making an unwarranted enumerative inference from a particular instance to a universal affirmative proposition (Blackburn, Problem of Induction, p. 184) – i.e. our behaviour is contingent on having mental states, therefore all such behaviour is a contingence of mental states. Furthermore, as the objection goes, it is not only an unwarranted inference but also a rather weak one at that, since our conclusion rests exclusively on a single, lonesome enumerative premise. This can be likened the conclusion that all aeroplanes are Lufthansa after only ever having seen one single aeroplane (Lecture 3, Lufthansa objection).

They are eating...the captain!

They are...eating...the captain!

Inference to the Better Explanation

However, the ‘Lufthansa problem of induction’ is hinged upon the twin assumptions that (a) there are numerous possible propositions, which could have been the case – i.e. a plethora of different airlines, which a plane could have belonged to, or a whole spectrum of colours a swan could have had – and as an extension of this that (b) we are indeed making an attempt at a sound argument for one of these uncountable propositions by enumerative inference alone.

Assuming outside-world realism we should be able to limit the possible propositions to only two – by the principle of excluded middle (Blackburn, p. 124) – and either assert the factuality of the other minds hypothesis or that of the zombie hypothesis. Any encountered non-illusory entity, which displays behaviour associated with agency of mind, must either possess such agency or be a zombie.

As such, the crux of the matter is not which hypothesis we are able to prove conclusively and irrefutably by inductive reasoning. We are not positing an isolated enumerative inference, but rather we are making an inference to the better of only two possible explanations (Herman, 1965). Granted, the single-mind solipsist might still appeal to the metaphysical and logical possibility of zombies, and thereby insist that we cannot know with absolute certainty that other minds exist.

Burden of Proof

However, this sets a rather disingenuous double standard. Surely the hypothesis of other minds does not only share exactly the same metaphysical and logical possibility, it also happens to be a confirmed nomological possibility. If the scarce quantity of enumerative premises to support an inferred conclusion is truly a problem for the other minds hypothesis, then it is even more so for the zombie hypothesis, which cannot boast even a single observation of the proverbial Lufthansa plane. The sceptic of other minds could always retreat behind an infinite regress of possibilities with an ever-increasing unlikelihood.

Nonetheless, one must then wonder – given that the realism of the other minds position is the most reasonable explanation – how come the realist should perpetually bear the burden of proof in the face of a barrage of ever more unreasonable challenges set forth by the fertile imagination of the sceptic? I would surmise that at some point it would be more than appropriate to shift the onus onto the sceptic to show that her arguments from fantasy are also nomologically feasible.


If the single-mind solipsist is unable to provide evidence of either the actual existence of a zombie or the nomological possibility thereof, then it is unclear to me why the onus should be on the realist of other minds to provide good arguments for their existence. By inference to the better explanation we have no reason to concede the possibility that seemingly intentional behaviour could be caused by anything other than the antecedent mental states comparable to our own mind. Each of us knows for a fact that at least one mind exists, while zombies remain fanciful speculation.

To refute the solipsist or the metaphysical idealist all that you have to do is take him out and throw a rock at his head: if he ducks he’s a liar. His logic may be airtight but his argument, far from revealing the delusions of living experience, only exposes the limitations of logic (Abbey, Desert Solitaire, 1990, p. 97).


Lecture handout:

Lecture 3: Other Minds


Harman, Gilbert (1965). “The Inference to the Best Explanation,” The Philosophical Review 74:1, 88-95.


Abbey, Edward, Desert Solitaire: a season in the wilderness, (Simon & Schuster: New York, 1990)

Blackburn, Simon, Oxford Dictionary of Philosophy, revised 2nd ed. (OUP: New York, 2008)

Wittgenstein, Ludwig, Philosophical Investigations, (Blackwell: Oxford, 1958)

Web Pages:

Kirk, Robert, “Zombies”, The Stanford Encyclopedia of Philosophy (Fall 2008 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/fall2008/entries/zombies/>.

Share and Enjoy:
  • Facebook
  • Twitter
  • Digg
  • StumbleUpon
  • Reddit

3 Responses to “Braaaains on a Plane”

  1. Great Post! I love to read articles that are informative and beneficial in nature. Thank You for sharing your knowledge.

  2. cheap oem says:

    A mio parere, si sono errati. Cerchiamo di discutere di questo. Scrivere a me in PM.

Leave a Reply to Sketch Sepahi