Having said that, we must beware of a tendency to denigrate life-forms which do not happen to possess mental states. The behavioural flexibility of even the humblest bacterium - as manifested in phenomena as varied as gene swapping, phenotypic plasticity, habituation, sensitivity, memory, and indirect stimulus-response coupling - is so vast that it has taken decades of research, by our brightest minds, to fathom it. The complexity of the behaviour of a single bacterium is awe-inspiring, even if we confine ourselves to one aspect, such as locomotion. A bacterium moves around by a form of screw propulsion, which was only discovered 400 years ago, by Leonardo da Vinci (Di Primio, Muller and Lengeler, 2000, p. 4). One could profitably spend a lifetime researching the behaviour of such an individual. Bacteria may lack awareness, but the tasks of what they can perform is very impressive, which is why Kilian and Muller (2001) propose copying some of their features to design technical artifacts.

A bacterium is, after all, a living thing. It has well-defined biological functions and an interest in realising these functions. It does not have a mind, but it still matters.

So far, our investigation has shown that even "simple" organisms already possess a high degree of adaptability as well as behavioural flexibility, which indicates that they need it in order to survive. If learning is not so prevalent among organisms, it is only because most organisms can cope perfectly well without it, thanks to a dazzling array of behavioural tricks. This behavioural repertoire is the platform which supports mental states:

Cognition, at least in Nature, can only exist in organisms that are able to live without it. In other words, cognition comes as an enhancement to existing mechanisms of action regulation, not as the sole means by which organisms control their behaviour (Strube, 1998, p. 90).