Are mind and brain on the same level? Mental properties and biological properties are so different that some kind of dualism is still an attractive position for many people. Intuitively, mental phenomena are often assumed to be on some kind of higher level than physical phenomena. For example, in order to accurately describe what it means to have compassion for another living being, most people would probably agree with the popular expression that this simply cannot amount to nothing but the description of the underlying neurophysiological activity or behaviour related to that compassion—that presenting the neurophysiological activity alone does not fully capture all properties of being in a state of compassion. Instead, especially in everyday life, we might rather refer to the phenomenological properties of compassion, the properties we draw on to identify that we are in a state of compassion at a given time. These properties seem to have a special value for us. In a way, they seem to be much richer than those of "cold" science. But what, exactly, does it mean to say that mental and physical phenomena are not on the same level? If I were to ask what compassion is, most people would probably agree that it is somehow realized by their body, just as an elaboration of this fact does not suffice for a complete description of compassion, implying that there must be something more than that, on a higher level. This, at least for a philosopher, inevitably leads to the question of what those levels actually are. What does “level” refer to? To what extent do levels exist in the world at all? These questions become even more pressing when we make ourselves aware of the extent to which the sciences use the concept of “level”. Whole disciplines, such as psychology and neuroscience, are distinguished as operating on different levels with different theories aiming at specific target phenomena. Levels also play a role within disciplines. In neuroscience, for example, it is quite common to distinguish between lower-level brain functions as realized in the brain stem or primary sensory areas as opposed to higher-level functions like decision-making or emotion regulation that are attributed primarily to the frontal lobe. Likewise, the distinction of processes and functions as operating “bottom-up” or “top-down” is quite prevalent.
There is a general strategy in science that has proven to be effective for explaining a certain phenomenon: decomposition. The reason for that is as follows: to fully explain a phenomenon, it does not suffice for us to be able to elaborately describe it or list certain correlations with singular components or other phenomena. Rather, we need to know in detail how the phenomenon comes into existence, based on how exactly it is realized: which components underlying the phenomenon are doing what, where, when, and how in order to make the phenomenon emerge. These requirements are captured excellently by Carl Craver’s (2007; Craver & Darden 2013, p. 15) famous definition of a mechanistic explanation:
mechadef/mechanistic explanation =Df [m]echanisms are entities and activities organized such that they are productive of regular changes from start or set-up to finish or termination conditions. (Craver & Darden 2013, p. 15)
But in what sense are the mechanistic components of a phenomenon on a lower level than the whole phenomenon? This is the question Craver answers in his article “Levels”, in this collection.
In what follows, I shall first point out I find most important about Craver’s account of levels of mechanisms and where I see some difficulties in his account. I shall then propose an alternative way of defining levels by emphasizing the notion of “properties”. The idea here is that levels are a direct result of property instantiations and thereby constitute “property-dependent epistemic dimensions”. By focusing on properties in general, and not only on properties of mechanisms, I hope to show that an account of levels does not have to be as restricted as Craver proposes. I shall also argue that levels of mechanisms and levels of emergence do not have to be conceived as necessarily distinct, but can rather be combined quite well into a productive account of mechanistic emergence. Expanding Craver’s account of levels this way provides not only a notion of levels with wider applicability but also builds on his account of mechanisms as operating on different levels, which instils explanatory potential into a contemporary account of emergence. This still secures the application of “levels” in science, but at the same time makes transparent how the epistemic contexts of science are property- and level-generative. The ultimate goal of this approach is, of course, to elucidate how one and the same material system may show significantly different properties to an extent that elicits serious confusions about matters of identity.