Are viruses aware? The question may seem a ridiculous one, but as the following report shows, even medical researchers are prepared to speak of viruses as being intelligent:

Are viruses alive? After more than 25 years of studying the tiny disease-carrying microbes, Michael Lai thinks so.

"Viruses are very intelligent. They can think. They do things that we do not expect. They adapt to the environment. They change themselves in order to survive," said Lai, professor of molecular microbiology and immunology and a Howard Hughes Medical Institute Investigator.

Viruses ... have evolved defenses to help them evade the immune system. Viruses that cause infection in humans hold a "key" that allows them to unlock normal molecules (called viral receptors) on a human cell surface and slip inside.

Once in, viruses commandeer the cell's nucleic acid and protein-making machinery, so that more copies of the virus can be made (Emerson, 1998).

The gist of the claim that viruses are intelligent is that (so far) some of them have managed to not only bypass our bodies' natural defences, but also to thwart the best scientific efforts to eradicate them.

A few brief comments are in order here. First, the fact that the behaviour of viruses can be described in cognitively rich metaphors does not establish that they are in fact intelligent. For that matter, we can use cognitive metaphors to describe the behaviour of metal alloys like nitinol (which can "remember" their former shape when deformed), or even atoms and molecules (which are "attracted" to one another).

More telling is the fact that viruses can be described using Dennett's intentional stance: they possess information (a "key") that enables them to enter and control their host, thereby achieving their goal (replication). Even though thermostats can be described using the same stance, a virus, unlike a thermostat, is alive (and hence, a potential candidate for mental states). However, it has been argued above (see Conclusion S.2) that our ability to describe an entity using the intentional stance is, by itself, not a sufficient reason for imputing cognitive mental states to it: a mind-neutral goal-centred intentional stance, which explains the behaviour of a virus in terms of its information and goals, is also possible. In keeping with the methodology I have proposed, an agent-centred mentalistic stance should not be adopted unless it enables us to make better predictions about viruses' behaviour.

S.3 Our ability to identify behaviour in an organism that can be described using the intentional stance is not a sufficient warrant for ascribing mental states to it.

Second, one reason why the behaviour of a virus is so reminiscent of intelligence is that it can adapt to changing circumstances by mutating rapidly. However, a new mutant is not the same individual as its progenitor. If we wished to impute intelligence to viruses, we would have to impute it to an evolutionary lineage, rather than a single organism. This contravenes Conclusion N.4, which stipulates that we must be able to identify intrinsic relations, dedicated functionality, and a nested hierarchy of parts, before ascribing cognitive mental states to an entity. An evolutionary lineage, unlike an individual organism, lacks all of these features.

N.5 An entity must be an individual biological organism in order to qualify as having cognitive mental states. An evolutionary lineage of organisms cannot be meaningfully described as having cognitive mental states.

Third, the rapid adaptability of viruses can be explained in computational terms. The claim by Wolfram (2002, pp. 720 - 721) that computational devices are ubiquitous in nature, and that practically any system is capable of performing the most sophisticated computations possible in our universe, puts the adaptability of viruses in perspective. A virus and its descendants can be seen as an extended computing device for computing solutions to biological problems, such as how to overcome the defences of the human body. As we have seen, our ability to describe an entity as a computational device does not warrant our ascribing mental states to it (Conclusion S.1).

Fourth, the computational metaphor allows us to have a better understanding of the behaviour of viruses than we would get by ascribing mental states (e.g. devious plans) to them. For example, the computational metaphor allows us to roughly predict how long it will take for a lineage of viruses to evolve resistance to a particular vaccine, based on their raw computing power.

Dennett (1997, pp. 109 ff.) has proposed that organisms, as intentional systems, can be thought of as occupying a number of different levels of cognition, each of which yields a different kind of mind. Each kind of mind has its own trial and error procedure for generating and testing improvements. The most basic kind of organism is a "Darwinian creature". A creature at this level is a product of nature, which selected its genes through the trial-and-error process we call the survival of the fittest. However, such a creature, Dennett claims, is "wholly designed at birth" (1997, p. 110): it cannot alter or improve its responses to its environment. At the Darwinian level, trial-and-error improvement can only occur when nature develops a new, fitter organism with "better" (more successful) genes.

Viruses can be thought of as Darwinian creatures, on Dennett's schema, but with one important qualification: their genotype (or genetic make-up) is not the only factor controlling their phenotype (visible physical properties). Viruses (and all other organisms) exhibit some degree of phenotypic plasticity, which can be defined as the ability of organisms with the same genotype to vary their developmental pattern, phenotype or behaviour in response to varying environmental conditions (Ancel and Fontana, 2002). For example, if the immune system of a virus's host responds in a variety of different ways to being attacked, those viruses which are more phenotypically plastic and can adapt better to a changing host response will be favoured by natural selection (Domingo, 1997, cited in Ancel and Fontana, 2002). Dennett's assertion (1997, p. 110) that improvement in fitness for the most basic kinds of organisms occurs only at the genetic level is thus incorrect.

So far, we have characterised viruses as being adaptive only as lineages, but the phenomenon of phenotypic plasticity is a kind of adaptability shown by individuals. It is perhaps the best prima facie candidate for intelligent behaviour in viruses.

A well-known case of phenotypic plasticity in viruses is the lysis-lysogeny decision, whereby parasitic lambda-phage viruses adopt a bet-hedging strategy in order to cope with fluctuations in the availability of their hosts (E. coli bacteria). Preuss (2000) describes the process thus:

When a bacteriophage ("bacteria eater") virus injects its own dna (sic) into a microorganism such as Escherichia coli, the host cell apparatus rapidly expresses the program on the viral dna (sic) that decides whether or not to kill the host immediately. Under conditions that are less than optimal for replication, the phage may actually confer immunity to further infection upon the host (lysogeny). But if conditions are good, the virus produces so many copies of itself that the cell walls burst - a state known as lysis - and the infection spreads.

Two independently produced regulatory proteins compete to control whether the invading genes will remain quiescent or be expressed. Because of inescapable thermal noise, the outcome in any given case is random, and the proportion of the population in either state changes according to conditions such as cell nutrition and the number of invading particles per cell...

Arkin and his colleagues have found that the underlying stochastic [i.e. random - V.J.T] mechanisms of the lysis-lysogeny decision circuit... depend entirely upon the chance timing and concentrations of bursts of competing proteins that act to reinforce or inhibit one another.

"...Thermal fluctuation at the molecular level makes for diversity in cells that start out under identical conditions," says Arkin. "The phage actually makes use of noise as a survival mechanism: sometimes it pays to multiply and infect as many hosts as possible, sometimes it pays to lie low. Either way, the viral population is prepared to cope with changing conditions" (italics mine).

The above article describes the viral DNA as making a decision. Should we take this literally? If not, why not?

First, the above behaviour does not seem to meet the criteria required for the adoption of Dennett's intentional stance. At the very least, viruses need to possess information that enables them to realise their goals. However, in this instance, we do not see viruses possessing (i.e. encoding or storing) information about environmental conditions conducive to replication, but simply responding to changing conditions.

Second, the behaviour displayed by the viruses is in no way self-initiated: it is driven entirely by environmental changes (thermal fluctuations). Before we can describe a piece of behaviour as a "decision", there has to be some kind of agency involved. At the very least, internal states of the organism (as well as external conditions) must influence the behaviour observed.

Finally, as the article states, it is random noise which determines whether the viral DNA is expressed or remains quiescent. It would be a misuse of the English language to describe this as a decision: decisions, by their very nature, require rational justification.

The foregoing discussion of phenotypic plasticity in viruses has yielded three further conclusions regarding mental states in organisms:

N.6 An organism must be capable of encoding and storing information about its environment before it can be said to possess mental states.(Corollary of Conclusion N.2.)

N.7 Behaviour by an organism must vary in response to its internal states, as well as external conditions, before it can be regarded as a manifestation of a cognitive mental state.

N.8 Behaviour by an organism must vary in response to non-random internal states before it can be regarded as a manifestation of a mental state.

The ascription of cognitive mental states to viruses is thus methodologically redundant, as we can explain even their most sophisticated behaviour without resorting to a mentalistic intentional stance. Since viruses are organisms (as we argued in chapter 1), we can formulate the following conclusion:

S.4 Being an organism is not a sufficient condition for having mental states.

Although there are no grounds for ascribing mental states to viruses, we should not under-estimate what they can do. They are organisms - i.e. bona fide selfish individuals with a telos - with highly specific built-in information about their hosts that enables them to pursue their goals. Because of their impressive computational abilities, they can, en masse, solve problems in a way that mimics intelligent behaviour. Finally, they possess built-in mechanisms that enable them to adapt their behaviour to changes in their environment. Although they do not exhibit true agency, they possess the platform on which it is built.