This, at least, is how observers typically interpret what they are seeing. The immune cell is presumably sensing and following a chemical trail of some kind exuded from the bacterium, but it is nigh impossible to watch the movie and not frame it mentally with the narrative of a predator and its prey, each trying to out-maneuver the other. The movie seems to validate what Austrian biologist Karl Ludwig von Bertalanffy (a founder of the discipline of general systems biology, which drew on ideas from thermodynamics and cybernetics) said in 1969: “you cannot even think of an organism… without taking into account what variously and rather loosely is called adaptiveness, purposiveness, goal-seeking and the like.” (Bertalanffy 1969).

Should we even try to do so? The narrative the mind imposes on Rogers’ movie feels dangerously anthropomorphic, seeming to attribute to mere cells the kinds of capacities and behavioural drivers we might normally associate with the world of large and cognitively complex animals. But it is not obvious why, if we are prepared to recognize purpose, goals and agency in our own behaviour, we should make it inadmissible for “simpler” organisms. Perhaps, rather than wondering if we are reading too much purpose and agency into the neutrophil chase, a better question is to ask how agency might manifest both similarly and differently at different scales in time and space.

The predominant tendency in modern biology is, however (and pace Bertalanffy), to deny any need to invoke agency at all – to suppose that cells and bacteria, and perhaps the vast majority of living things, can be regarded as sophisticated machines. As Walsh (2015) says, “Organisms are fundamentally purposive entities, and [yet] biologists have an animadversion to purpose.”