Recently I discussed a framework to study consciousness in animals (Van den Bos 2000).

This framework comprised:

• i) a hierarchical negative feedback model of the central nervous system in which behaviour is the control of input (perception) expressed as transitions of behavioural patterns (= motion) and as transitions of mental states (= consciousness; Van den Bos 1997). Consciousness is hypothesized to be a property of neuronal networks of self-organizing systems dedicated to dealing with rapidly-changing environments affording flexibility of behavioural patterning;

• ii) mental states - mental representations - as intentional states as described in folk psychology (feelings, desires; beliefs, insights, etc);

• iii) the separation of mental states into two components, an invariant part (‘the presence as such’; that) and a variant part (‘the way it looks’; how), which are separately related to the organization of the central nervous system, ie a ‘neuronal network’ and ‘momentary active connections within the neuronal network determined by input and output of this neuronal network’ respectively;

• iv) the idea that every mental state (psychological trait) - whether feelings, desires or beliefs - can be viewed conceptually as the product of a specialized neuronal network and information encoded in the network (neuronal input-output relations) which is expressed as a specific series of spontaneous behavioural patterns or in specific tests; and

• v) a phylogeny based on the invariant part, ie mental states, and the presence of a neuronal network.

It is my conviction that all animals, including invertebrates, possess a mind. This conviction is not based on scientific evidence. We are unable to observe the mind directly. According to the principle of parsimony, I assume that body and mind are two aspects of the same. This assumption predicts that it will always be possible to find a bodily explanation, implying that it will never be possible to perform an experiment that proves that a mind is present in any animal species, including human beings. As a result, it will never be possible to prove scientifically that my conviction that all animals possess a mind is correct or wrong.