Abstract

LOTTER, Hennie. Putnam's flawed modelling in his brain-in-a-vat thought experiment. Tydskr. geesteswet. [online]. 2020, vol.60, n.4-2, pp.1295-1316. ISSN 2224-7912.  http://dx.doi.org/10.17159/2224-7912/2020/v60n4-2a11.

Could it be that the debate about Putnam's famous brain-in-a-vat (BIV) thought experiment has not yet reached an end? Is it possible that someone could still say something new about such a stunning philosophical essay that had a major impact across different philosophical fields? In a recent collection of fourteen essays, focussing exclusively on Putnam's BIV essay, Gila Sher raises a "new question" about Putnam's BIV thought experiment, endorsed by the editor (Sandberg 2016:16), but without offering an answer. She Asks: "Given that it ispossible that BIVs exist, is it possible that under certain conditions they will have some genuine knowledge of the world, and if so, what kind of knowledge and under what conditions?" (Sher 2016: 208) In this essay, I offer an answer to this question. I do so in the following way. I first explain the two main issues driving Putnam's brain-in-a-vat thought experiment. I set out the challenge of philosophical scepticism and then I explain what Putnam's theory of semantic externalism involves. His theory of semantic externalism informs the way that he intends to resolve the philosophical issue of scepticism. Putnam targets one premise of philosophical scepticism, i.e. that if we were brains in a vat, then we would not be able to distinguish between [i] our experiences of ourselves and our own situation in our world and [ii] what our situation would have been like ifwe were living as brains in vat. I next show how Putnam constructs the challenge that the BIV thought experiment offers. Putnam uses his theory of semantic externalism, coupled with a very specific design of the brain in a vat thought experiment, to argue that brains in a vat cannot make a meaningful, referential claim that they are brains in a vat, as their language does not refer to any objects in the real world, or the brain-in-a-vat world. I demonstrate (i) how he makes a core assumption about the exclusive role of sensory observation in developing his BIV thought experiment and (ii) how I intend to challenge that assumption. Putnam assumes that the human mind has "no access to external things or properties apart from that provided by the senses" (Putnam 1981:16). This assumption is crucial for Putnam's definition of the lack of access that BIVs have to an extra-linguistic reality, as they possess no senses. However, note what Putnam does. He equates access to an extra-linguistic reality to getting to know "external things and properties" through our five senses. My claim is that Putnam works with a restricted, uncritical assumption about the sensory capacities of human brains. He assumes we have five senses that give us perceptions about phenomena, events, processes, and occurrences that come from outside ourselves, i.e. from outside our minds, brains, and bodies. He ignores perceptions and experiences that are generated within our bodies and brains, and registered and recorded by organs other than the traditional five sense organs. This omission is the cause of a flawed imaginary thought experiment that distorts it and disrupts the success of the conclusions he draws from his BIV thought experiment, or so I argue. I claim that equating extra-linguistic reality with "external things and properties" is mistaken. If I am correct, then Putnam cannot reasonably conclude that "there is no basis at all for regarding the brain in a vat as referring to external things" (Putnam 1981:14). If my claim is true, Putnam's argument against scepticism suffers a blow and the spectre of sceptical doubt comes alive again, i.e. whether we ourselves are brains in a vat - as it seems logically possible that we might be BIVs. I next analyse the philosophical style of his BIV thought experiment to find a criterion embedded in this style for judging the appropriateness of his BIV thought experiment. I use literature on models and thought experiments to determine what the criteria for adequate, appropriate modelling are. Thereafter I examine the style of philosophy he uses, as the result of this examination of his philosophical style offers criteria for the evaluation of the BIV thought experiment. Then I show how he constructs his argument to prepare the ground for the introduction of the BIV thought experiment. The examination of the style and build-up of the BIV essay will enable me to pinpoint the flaw in his overall argument. I demonstrate how the BIV essay is mainly constructed to address his claims about semantic externalism, and as a consequence of making that point, Putnam then applies it to the problem of scepticism. I show how Putnam modifies the brain-in-vat thought experiment to make it a stronger challenge in terms of scepticism. Putnam constructs a possible world for his brains in a vat (BIVs) to demonstrate that they cannot ever say that they are brains in a vat, as their language never acquires referential functions due to its lack of contact with an extra-linguistic reality. If they were to say: "We are brains in a vat", that proposition would be self-refuting (Putnam 1981:7-8). Based on the results of the sections above, I pinpoint the shortcoming in his argument against scepticism. The shortcoming is his inadequate modelling of the brains in a vat. I then challenge the BIV thought experiment by demonstrating that BIVs have the capacity to outsmart the automatic machinery (his super-computer), given the qualities that humans possess and that Putnam should have properly embedded and activated in the BIV thought experiment. In particular, I demonstrate why BIVs can be thought to have a meaningful language, one sufficiently meaningful for Putnam to be able to have a phone conversation with them. Next, I demonstrate the possibility that their meaningful language has the potential to acquire reference. I illustrate how such acquisition of referential functions might plausibly occur. Once those possibilities have been shown, I argue that Putnam's modelling of the human brain is inadequate, as he has neglected to embed core features of human brain functioning in his modelling of the brains in a vat. I use knowledge of the functioning of human brains to support these arguments. I finally discuss the implications of my demonstration of the shortcomings of Putnam's construction of the BIV thought experiment. These implications point to the fact that humans, properly modelled, are much smarter than Putnam demonstrates through his BIV thought experiment. I claim that as humans, we might possess the requisite intellectual capacities to identify ourselves accurately as brains in a vat - and to express that knowledge in meaningful, referential language. In this way, humans are smart enough to reject one of the premises of the sceptical argument, i.e. that we cannot distinguish (i) our knowledge of ourselves, our specific situation and our current circumstances from (ii) the knowledge we would have had of ourselves, our specific situation, and our current circumstances, if we were brains-in-a-vat.

Keywords : Putnam; brain-in-a-vat; skepticism; thought-experiment; modelling; semantic externalism; reference.

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