A central problem in philosophy is that of other minds. How can we know for certain that other minds exist, and that people are not merely automatons? And if other minds do exist, how can we know their exact nature? For it seems that, although we may surmise their nature by the accounts of others, there is no way that we can fully rely on the testimony of others, given that a lot is not only lost in translation, but inexpressible in words. The argument from analogy is one attempt to demonstrate that other minds do exist.
J. S. Mill formulated a version of the argument in An Examination of Sir William Hamilton's Philosophy. In it, Mill states that, by an examination of his own case, it is clear that feeling is created by an antecedent condition, and results in a subsequent action. For example, when I fall down and hurt my leg, the first thing that happens is that my leg is physically affected (the antecedent condition). A split-second later, I feel this in my mind. Subsequently I express this in my outward demeanour. Therefore, there are three steps involved wherever feeling is concerned.
Mill notes that only the first and last of these steps is observed in other people: you may see another person fall down and hurt his leg then express pain, but there is no empirical evidence to suggest an intermediate stage. In Mill's own experience the antecedent condition could not produce the subsequent reaction without the transitional stage, therefore he is forced to conclude that there is one in others, and that it must be the mind. That the link happens to be the mind is not a necessary conclusion, but for all intents and purposes is the conclusion that Mill prefers.
It is clear that the argument from analogy largely arises from common-sense, and puts little effort into withstanding philosophic scrutiny. The most notable weakness, it seems, is the idea that there must be a mind in others, simply by virtue of there being antecedent conditions and subsequent reactions. Where common-sense tells us that this is most likely to be the case, logical enquiry begs the question: must there be an intermediate stage? And if so, is it necessarily the mind? If there were no intermediate link, then this would certainly make others automatons, and therefore we can put that possibility aside because it runs contrary to instinct. However, there is no evidence, empirically at least, that this link is the mind.
In any sound empirical argument, it is necessary to take evidence from as many examples as possible - the more examples that agree with one's hypothesis, the more one can trust the validity of the hypothesis. This, however, is impossible in the case of the mind, because my notion of mind comes only from experience of my own mind, and from the fact I have privileged access to it. We can say with certainty that all people have brains because this is evident from the work of many scientists and anatomists, but our understanding of how the brain creates consciousness (assuming that it does) is very limited, and hence the existence of brains does not entail the existence of minds.
Even if I assume that others do indeed have minds, the argument from analogy does not go to any lengths to describe the nature of these other minds. Let us imagine a hypothetical situation in which a robot were made to replicate human actions and words convincingly. If we saw such a robot not knowing what it was, we would be inclined to think it were human. But robots, although they can be programmed to, for example, recognise the taste of cheese by detecting its chemical composition, would not be able to qualitatively taste the cheese. Therefore a robot, even if it could converse intelligently, would not have a mind in the same sense that I have one, merely a central processing unit. Furthermore, even assuming that other minds do exist and that they experience the world in some sense qualitatively, this hardly guarantees a similarity between other minds and my own. When I see the colour blue, I recognise it as blue in a qualitative sense. From experience I know that others also recognise blue, since they agree with me that it is blue. However, since only they have privileged access to their minds, I can have no conception of precisely how they see blue.
Since the idea of mind is inextricably tied with privileged access, a difficult concept to get around, some philosophers (mainly J. B. Watson and B. F. Skinner) have opted to avoid these difficulties by simply bypassing the intermediate link. "Behaviourism" regards mind as a non-separate entity, because for scientific purposes, it claims, the mind does not exist. Humans merely behave, or act, upon a disposition to act. Therefore a desire for beer, for example, is the disposition to drink beer. Since one cannot know whether someone desires to drink beer without them actually drinking it or expressing their desire for it, as far as we know their desire does not exist independently from these actions.
If actions are just the result of dispositions to act, there is no need to suggest that others have minds at all; they need only have a primitive brain which feels physical pain and desires things. However, this theory seems woefully inadequate as an account of mind. How, for instance, do we account for those beliefs and desires which are not expressed physically or verbally? A belief in God need not be expressed by prayer or by confession, and yet palpably it exists in many people.
On the other hand, Mill's argument from analogy, as we have seen, does little to explain the nature of other minds. A central premise of the argument is Mill's observation that others have bodies. While doing away with Cartesian mind-body dualism in one fell swoop, this seems nevertheless to belittle the idea of the mind, limiting it only to the physical sphere. While it is true that in our experience the mind is inseparable from the body, there is no absolute rule that states that minds generally must have a body. It can be said, for instance, that senses such as sight and hearing are illusions, since they operate solely on signals sent from the eyes and ears. If a scientist managed to take someone's brain from their body and, by replicating the signals from the eyes and ears gave the brain the illusion it was seeing and hearing, then it seems that brain would contain no less of a mind than any other.
Instinct and common-sense tell us that others do have minds. However, philosophy seeks not to make any assumptions, and we cannot assume that common-sense is correct and certainly not that it tells us enough. The argument from analogy is a common-sense approach that seems rather out of place in philosophy, mainly because it is not rigorous or detailed enough to stand up. I don't doubt that other minds exist, but Mill's argument cannot be regarded in any way as proof. Further, since it is does not give a satisfactory definition of mind, there is no way I can be certain that others possess minds as I know them, and therefore I cannot even venture to give them the title of minds.
