In his paper ‘Is there a Fundamental Level?’ (2003), Jonathan Schaffer makes a comprehensive case that belief in a fundamental level is unjustified for all the different senses of levels. He introduces the idea of a fundamental level as follows:
‘Talk about ‘the fundamental level of reality’ pervades contemporary metaphysics. The fundamentalist starts with (a) a hierarchical picture of nature as stratified into levels, adds (b) an assumption that there is a bottom level which is fundamental, and winds up, often enough, with (c) an ontological attitude according to which the entities of the fundamental level are primarily real, while any remaining contingent entities are at best derivative, if real at all. (2003, p. 498).
His paper takes issue with (b), the assumption of a basic level, and argues that it is unwarranted. The question of the existence of a basic level – and our motivation and justification for believing in one – arises for each of the senses of levels (mereological, supervenience etc.) that we’ve considered. It may be that the levels comport, but if they don’t, there may be a fundamental level in some senses and not in others. For example, matter might be infinitely divisible compatibly with there being a fundamental supervenience base – say if the parts below a certain level are boring in the sense that they supervene on the wholes. So really there is not one but several questions about a fundamental level.
For levels in the mereological sense, the idea of a basic level is widespread, but as Schaffer points out, many scientists and philosophers have also thought about matter as infinitely divisible into smaller and smaller parts, and there is nothing a priori wrong with this picture.21 The question of the existence of a basic level is an empirical one.
For levels in the supervenience sense, the idea of an ultimate supervenience base for everything is presumably equally widespread, and might be correct even if mereological fundamentalism is wrong. But its correctness is not beyond doubt. For example, it would be wrong if supervenience and mereological levels comport, and higher levels supervene on ever-deeper levels on the infinite divisibility picture.
How about ‘levels’ related as roles and realisers? The traditional functionalist picture described in section 1 needs the presupposition of a basic level. Higher ‘levels’ or ‘orders’ of properties are properties of having certain properties of another kind: real properties that can do causal work. And while some role properties may be realised by further role properties, there must be a basic level where the instances that make true the implicit quantifications in the role properties are found. It might perhaps be possible to construct a version of functionalism (or something close) that will work without the presupposition of a basic level, but it would have to be very different from functionalism as traditionally understood.
For levels of objects related by the constitution relation, the issue of a basic level does not seem crucial; here, the significant distinction is between one level and more than one level (i.e. more than one object to a place).
In the following, we shall concentrate on the two first senses of levels: the mereological and supervenience senses.
Schaffer (2003) argues that the presupposition about a basic level is unwarranted both in the mereological and the supervenience versions. The main problem with level fundamentalism in both versions is that unwarranted empirical presuppositions are made. In the mereological case, Schaffer takes the reasoning to be something like this (these presuppositions are the only ones that would warrant the fundamentalist’s claims):
1) There will be a complete microphysics,
2) the complete microphysics will postulate particles, and 3) these particles are the mereological atoms.22
In the supervenience case, similar presuppositions are needed: 4) There will be a complete microphysics,
5) it will describe a comprehensive supervenience base, and 6) this will license supervenience-only fundamentality.23
22
Schaffer (2003), p. 502.
23
In both cases, the reasoning is flawed, simply because we don’t have a reason to believe that there will be a complete microphysics. Science might continue to make progress without ever reaching a point at which the job is finished (or it might end or go astray before the goal is reached). 2) and 3) are also unjustified, as there is no telling what a complete microphysics will say until we’ve discovered it. Scientific development is notoriously unpredictable, and there is no guarantee that we have got the basic terms (e.g. particles) right yet. Also, many times scientists have believed we have found the ‘atoms’, only to discover that these, too, have parts; if history suggests anything, it is that the idea of smallest particles is a presupposition of ours; it is certainly not something we have empirical reasons to believe in.24
For the supervenience case, the situation is a little better, as 5) and 6) are more plausible than 2) and 3). According to Schaffer, what defines a complete microphysics is that it tells a complete causal story, and a complete causal story will also serve as a complete supervenience base.25 So 5) is warranted given 4), and is correctly neutral on what a complete microphysics would say. And 6) follows from
5); if we have a comprehensive supervenience base, then this licenses
fundamentalism in the supervenience sense (but not in the mereological sense; the ultimate supervenience base might well be an intermediate mereological level). Supervenience-only-fundamentalism thus depends on fewer doubtful assumptions than mereological fundamentalism: all that is needed is the presupposition about a complete microphysics, while the view can remain (correctly) neutral on the basic terms of that completed science, and on the issue of infinite divisibility. But still, both versions depend on an unwarranted assumption.26
24
This paragraph is based on Schaffer (2003), p. 503-5.
25
One might object that causation, like particles, might be one of the components that do not make it into completed science; who knows what completed science will be like? Dialectically, this does not damage Schaffer’s argument, since it would make it even harder for the proponent of supervenience-only fundamentality to prove her point. Also, from the perspective of our current knowledge, the ’full causal story’ component seems more likely to make it into completed science than the idea of fundamental particles. So supervenience-only-fundamentalists are still better off than mereological fundamentalists.
26
Schaffer concludes that we should distinguish three different metaphysical pictures: infinite divisibility (the negation of mereological fundamentality),
supervenience-only-fundamentality, and full-blown (mereological plus
supervenience) fundamentality. If we keep discovering novel structures on deeper levels, that would constitute defeasible evidence for infinite divisibility. If we discover a complete microphysics, supervenience-only-fundamentality will be justified (in Schaffer’s view, this is the only ‘expensive’ empirical assumption supervenience-only-fundamentality requires). And if that microphysics postulates mereological atoms, then full-blown fundamentality will be justified. But until then, we have no reason to assume that there is a basic level.
Schaffer comes close to suggesting that, given no guarantee that there will be a complete microphysics, we should suppose infinite divisibility (‘if we keep finding new levels with novel ontological structures, then that suggests infinite divisibility’). But given our current state of knowledge, agnosticism seems the proper attitude to the question of a fundamental level.
The issue deserves a lot more attention. With the exceptions mentioned, I find Schaffer’s arguments convincing. But this brief discussion is aimed mainly to show that the presupposition of a basic level, in the supervenience or mereological versions, requires further justification.
4.1 Level fundamentalism and high-level locations
The question of a fundamental level is dialectically important when assessing the potential of theses of high-level location, including response-dependence theses. As Schaffer points out, level fundamentalism naturally gives rise to an attitude of inequality between levels. The idea of a basic level with a privileged ontological status might cast doubt on the importance of higher levels altogether. In the light of this picture, higher levels might be thought of as non-existent by one of the routes considered in the previous section (identification, reduction, or elimination). Or they may just be thought of as somehow less real and less important than the basic level. This would make theses of high level location, e.g. response-dependence theses, a lot less interesting than they might have seemed.
More concretely, the idea of a fundamental level plays a crucial role as backdrop for two standard argument types for low level locations: Arguments from ontological economy and causal exclusion arguments.
Reduction of one level of properties to another might seem to have a pay-off in terms of ontological economy even without the presupposition of a basic level. Reducing one class of facts to another is an achievement no matter what happens with other types of facts. However, if there are infinitely many levels, the achievement will be a lot less significant than if we are dealing with a limited number of levels; one step down an infinite road doesn’t do much good. If, on the other hand, we can reduce the levels one by one with the prospect of reducing everything else to a single level of well-understood facts, there is a real point to the reductions. This is how arguments from ontological economy depend on level fundamentalism.
Causal exclusion arguments rely even more heavily on the idea of a basic level. They entail that any level of properties or objects will be causally superfluous if there is a lower level to which the causal work can be attributed. The line of thought can be summed up as follows:
1. The disputed phenomenon (say, mental states) can cause low level events, 2. any low level event has a sufficient low level cause, and
3. no causal over-determination is at play,
4. so a low-level location should be chosen over a high-level location that would render the disputed phenomenon causally impotent.
If this argument works, then high-level locations will be incompatible with causal efficacy, and so will often be unattractive. However, if there is no basic level, the outcome may be very different. If the hierarchy of levels continues down ad infinitum, and if the argument can be repeated for each level, transferring the causal powers to the level below it (as Block and others have argued27), it would seem that ‘the causal powers would drain away down a bottomless pit’ (Kim’s phrase).28 No level would be doing the causal work. So either there is something wrong with the
27E.g. Block (1995).
argument, or there has to be some principled reason to stop the regress at some point, or causation must be an illusion.
An advocate of the causal exclusion argument might take the problem with causal drainage to show a priori that there must be a basic level. After all, we are pretty certain that there is causation going on in the world, and if the idea of infinite descent would conflict with this commonplace, then so much the worse for the idea of infinite descent. This just shows that there must be a basic level to hold the causal powers. This line of thought (along with other a priori arguments for the existence of a basic level) strikes me as misguided. The question about the existence of a fundamental level (in every sense of levels) is presumably an empirical one, as Schaffer points out, and this kind of a priori reasoning seems the wrong kind of evidence for a conclusion on the matter. If the causal exclusion argument depends on the presupposition of a basic level as an a priori matter, this suggests that something is wrong with the argument, even if we can’t say exactly what it is.
The issue of causal exclusion and drainage deserves a longer discussion that, again, we shall have to cut short.29 The important point for our purposes is that the presupposition of a fundamental level plays a crucial role in arguments for low level locations. If this presupposition is flawed, that makes high level locations such as response-dependence theses a lot more attractive. Schaffer has made a convincing case that the presupposition of a basic level is a lot less secure than people seem to think. So to the extent that levels fundamentalism fuels scepticism about high level locations, that scepticism seems unwarranted.