by Rishidev Chaudhuri
To my mind, the most fascinating biological systems lie in the uncanny interstices between the physical and the intentional, between systems that can be understood as purely material objects, in the mould of physics or chemistry, and those that seem to require some notion of self (and other) or intentionality or that use complex regulatory loops to maintain themselves as some sort of consistent entity. For example, how should we make sense of the immune system which, on the one hand, seems obviously physical (and hence avoids the debates associated with consciousness) and yet seems to contain at least a primitive notion of self and other, that maintains representations of and long-term memories about its environment and that seems to regulate in a way that feels teleological (or most easily understood this way). These systems challenge us theoretically partly because they are fiendishly complicated, typically consisting of many interacting parts and levels of interactions. But more than this, these parts and levels of interactions seem to form a consistent whole in a way that, say, a gas in a box doesn't, and in doing so they elude our theoretical frameworks. It's not that we know what a good theoretical description would look like and haven't found it yet1. Instead we seem to lack the right level of general principles of understanding and organization. At some point the principles we use to understand physical bodies (energy, entropy, conservation laws and so on) seem to break down, but the principles that we use to understand other subjects in the world (desires, goals, representation and such) don't yet hold. Thus these are material collections that are simultaneously coherent entities, inextricably embedded in the world and insensible without it. At the risk of sounding like one of those Continental metaphysicians whom physicists are always raising their eyebrows at, much of what is exciting about this realm is that it hints at new metaphysics, new categories of making sense of what a system is, what a meaningfully describable entity is, and so on. And reassuringly, these theoretical projects are anchored in the study of physical systems; this doesn't guarantee truth but does provide a set of constraints that nudge speculation in interesting directions.
