Weismann, Wittgenstein and the homunculus fallacy

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Abstract

A problem that has troubled both neo-Darwinists and neo-Lamarckians is whether instincts involve knowledge. This paper discusses the contributions to this problem of the evolutionary biologist August Weismann and the philosopher Ludwig Wittgenstein. Weismann discussed an empirical homunculus fallacy: Lamarck’s theory mistakenly presupposes a homunculus in the germ cells. Wittgenstein discussed a conceptual homunculus fallacy which applies to Lamarck’s theory: it is mistaken to suppose that knowledge is stored in the brain or DNA. The upshot of these two fallacies is that instincts arise through a neo-Darwinian process but are not cognitions in the sense that they involve (the recollection of stored) knowledge. Although neo-Lamarckians have rightly argued that learning processes may contribute to the development of instincts, their ideas about the role of knowledge in the evolution and development of instincts are mistaken.

Introduction

Instincts fascinate biologists, psychologists and philosophers for two interrelated reasons. First, instincts seem to guide organisms through a complex natural and social world and contribute, therefore, to the harmony between an organism and its environment. Yet how can we understand this apparent harmony between instinct and environment? Two opposing explanations are distinguished (cf. Jablonka & Lamb, 2005). Neo-Darwinists suggest that instincts evolve as the result of natural selection and reject Lamarck’s theory on the inheritance of acquired characters. The harmony between organisms and their environment is according to them explicable as an evolutionary adaptation. Since instinctive behaviours evolve as the result of selection on genetic variation, they are according to neo-Darwinists innate rather than learned. They develop during the lifetime of an individual as the result of decoding of information in the genome. Neo-Darwinists assume that future investigations will provide more insight into the nature of this ‘phylogenetically acquired information’. Neo-Lamarckians, however, argue that instincts may also evolve as the result of instruction. They argue that learning processes are involved in both the development and evolution of instincts. Neo-Lamarckians assume that future studies will provide insight in how instinctive behaviour displayed by organisms in the present generation is, in part, the product of the accumulated experiences of past generations fixated in developmental programs. Secondly, instincts appear to involve knowledge, for animals seem to know what an appropriate act is in a given situation. For instance newborn animals instinctively appear to know how to (re)act in a certain situation, since they immediately use their limbs in a purposeful manner and act without hesitation. As Bonner (1974, p. 47) put it, ‘the animal is born with a memory of how to do something that it has never done before’. Again, it is assumed that future studies will show how animals are able to act on the basis of this knowledge stored in the DNA or in developmental programs. In the case of the human species, these investigations are extended with studies into the language instinct (cf. Pinker, 1994). Hence the problem arises how we can investigate the apparent harmony between linguistic behaviour and the world as an extension of the harmony between instinct and the world.

In this paper I will discuss the contributions to our understanding of the harmony between instinct, knowledge and the world of the evolutionary biologist August Weismann and the philosopher Ludwig Wittgenstein. The reason why I discuss their contributions is that both have discussed homunculus fallacies. Weismann criticized Lamarck’s theory of evolution since Lamarck presupposes according to Weismann the existence of a homunculus in germ cells; Wittgenstein criticized theories that explain the apparent harmony between knowledge (or language) and the world by referring to information stored in the mind, brain or DNA, since these theories mistakenly assume that cognition can be attributed to parts of a living organism (as if these parts are homunculi). I argue that Wittgenstein’s ideas can be seen as an extension of those of Weismann. Hence the combination of their ideas, I suggest, sheds new light on the old problem of the harmony between instinct, knowledge and the world.

Section snippets

Weismann on instinct

Weismann is well known because of his critique of the idea of Lamarck (accepted by Darwin) that instincts arise and decline from habit in use and disuse. In his critique, Weismann focused on the problem of how an acquired habit can become heritable. An acquired habit affects the somatic cells of the body, but in order to become heritable, there have to be changes in the germ cells as well, since offspring originate from the germ cells. It is, according to Weismann, possible that the environment

Innate or learned

Within the confines of the conceptual framework discussed by Weismann, there are still some conceptual (and, of course, many empirical) problems to solve. For instance: the adaptiveness of instinctive behaviour was used by Weismann as an effective argument against the theory of Lamarck. Yet if instinctive behaviours are selected adaptations and if the determinants underlying these behaviours are transmitted from one generation to the next through the immortal germ line, does this imply that

Instinct and the central dogma

After the discovery of DNA replication and the processes of transcription and translation involved in protein synthesis, Weismann’s ideas have been re-interpreted in terms of molecular genetics (see for instance Maynard Smith, 1986, Ch. 2). There is a specific reason why Weismann’s arguments were reconsidered. Weismann thought that, when embryonic cells divide, each daughter cell receives a different set of determinants, and used this hypothesis to explain cell differentiation (the development

Facts of mind and matter

The Lamarckian Spalding (1954 [1873], p. 8) believed that ‘instinct in the present generation is the product of the accumulated experiences of past generations’. However, Spalding noted that this hypothesis is not generally appreciated for conceptual reasons. The reason why investigators doubt the validity of the hypothesis is, according to Spalding, that the mind is involved:

The facts of mind  differ from material things in this important respect, that whereas the latter can be stored up,

Instinct, knowledge and abilities

We make a conceptual distinction between innate and acquired abilities (cf. Bennett & Hacker, 2003, Ch. 5). Examples of innate abilities are the ability to breathe, to perceive and to move one’s limbs. The ability to walk is an acquired ability, for we learn to walk. Yet although it is an acquired ability (and an example of a two-way ability, for we can choose whether we will walk), learning to walk does not involve the acquisition of knowledge. We do not possess knowledge after we have learned

Behaviour, brain and mind

Weismann illustrated his objections against the theory of Lamarck with the example of an actor. It is according to him for biological reasons implausible to suggest that alterations of memory-cells in the brain (as the result of memory-exercises of the actor) cause adaptive changes in the determinants present in the germ cells. Since Weismann’s example involves knowledge, it invites the conceptual problem how we can investigate the role of ‘memory cells’ in the retention of knowledge. For an

Conclusions

The combination of Weismann’s and Wittgenstein’s ideas clarifies our understanding of the harmony between instincts, knowledge and the world. Weismann has argued that the ideas of Lamarck are false since Lamarck’s theory tacitly presupposes that the determinants in the germ cells are miniature memory cells. It is therefore according to Weismann unlikely that there are corresponding effects in the brain and germ cells as the result of the memory exercises of an actor. The upshot of Weismann’s

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