One of the oldest questions in the theory of value is that of whether there is more than one fundamental (intrinsic) value. Monists say “no”, and pluralists say “yes”. This question only makes sense as a question about intrinsic values; clearly there is more than one instrumental value, and monists and pluralists will disagree, in many cases, not over whether something is of value, but over whether its value is intrinsic. For example, as important as he held the value of knowledge to be, Mill was committed to holding that its value is instrumental, not intrinsic. G.E. Moore disagreed, holding that knowledge is indeed a value, but an intrinsic one, and this expanded Moore’s list of basic values. Mill’s theory famously has a pluralistic element as well, in contrast with Bentham’s, but whether Mill properly counts as a pluralist about value depends on whether his view was that there is only one value — happiness — but two different kinds of pleasure which contribute to it, one more effectively than the other, or whether his view was that each kind of pleasure is a distinctive value. This point will be important in what follows.
2.2.1 Ontology and Explanation
At least three quite different sorts of issues are at stake in this debate. First is an ontological/explanatory issue. Some monists have held that a plural list of values would be explanatorily unsatisfactory. If pleasure and knowledge are both values, they have held, there remains a further question to be asked: why? If this question has an answer, some have thought, it must be because there is a further, more basic, value under which the explanation subsumes both pleasure and knowledge. Hence, pluralist theories are either explanatorily inadequate, or have not really located the basic intrinsic values.
This argument relies on a highly controversial principle about how an explanation of why something is a value must work — a very similar principle to that which was appealed to in the argument that intrinsic value must be an intrinsic property [section 2.1.1]. If this principle is false, then an explanatory theory of why both pleasure and knowledge are values can be offered which does not work by subsuming them under a further, more fundamental value. Reductive theories of what it is to be a value satisfy this description, and other kinds of theory may do so, as well (Schroeder ). If one of these kinds of theory is correct, then even pluralists can offer an explanation of why the basic values that they appeal to are values.
2.2.2 Revisionary Commitments?
Moreover, against the monist, the pluralist can argue that the basic posits to which her theory appeals are not different in kind from those to which the monist appeals; they are only different in number. This leads to the second major issue that is at stake in the debate between monists and pluralists. Monistic theories carry strong implications about what is of value. Given any monistic theory, everything that is of value must be either the one intrinsic value, or else must lead to the one intrinsic value. This means that if some things that are intuitively of value, such as knowledge, do not, in fact, always lead to what a theory holds to be the one intrinsic value (for example, pleasure), then the theory is committed to denying that these things are really always of value after all.
Confronted with these kinds of difficulties in subsuming everything that is pre-theoretically of value under one master value, pluralists don’t fret: they simply add to their list of basic intrinsic values, and hence can be more confident in preserving the pre-theoretical phenomena. Monists, in contrast, have a choice. They can change their mind about the basic intrinsic value and try all over again, they can work on developing resourceful arguments that knowledge really does lead to pleasure, or they can bite the bullet and conclude that knowledge is really not, after all, always good, but only under certain specific conditions. If the explanatory commitments of the pluralist are not different in kind from those of the monist, but only different in number, then it is natural for the pluralist to think that this kind of slavish adherence to the number one is a kind of fetish it is better to do without, if we want to develop a theory that gets things right. This is a perspective that many historical pluralists have shared.
The third important issue in the debate between monists and pluralists, and the most central over recent decades, is that over the relationship between pluralism and incommensurability. If one state of affairs is better than another just in case it contains more value than the other, and there are two or more basic intrinsic values, then it is not clear how two states of affairs can be compared, if one contains more of the first value, but the other contains more of the second. Which state of affairs is better, under such a circumstance? In contrast, if there is only one intrinsic value, then this can’t happen: the state of affairs that is better is the one that has more of the basic intrinsic value, whatever that is.
Reasoning like this has led some philosophers to believe that pluralism is the key to explaining the complexity of real moral situations and the genuine tradeoffs that they involve. If some things really are incomparable or incommensurable, they reason, then pluralism about value could explain why. Very similar reasoning has led other philosophers, however, to the view that monism has to be right: practical wisdom requires being able to make choices, even in complicated situations, they argue. But that would be impossible, if the options available in some choice were incomparable in this way. So if pluralism leads to this kind of incomparability, then pluralism must be false.
In the next section, we’ll consider the debate over the comparability of values on which this question hinges. But even if we grant all of the assumptions on both sides so far, monists have the better of these two arguments. Value pluralism may be one way to obtain incomparable options, but there could be other ways, even consistently with value monism. For example, take the interpretation of Mill on which he believes that there is only one intrinsic value — happiness — but that happiness is a complicated sort of thing, which can happen in each of two different ways — either through higher pleasures, or through lower pleasures. If Mill has this view, and holds, further, that it is in some cases indeterminate whether someone who has slightly more higher pleasures is happier than someone who has quite a few more lower pleasures, then he can explain why it is indeterminate whether it is better to be the first way or the second way, without having to appeal to pluralism in his theory of value. The pluralism would be within his theory of happiness alone."
-Schroeder, Mark, "Value Theory", The Stanford Encyclopedia of Philosophy (Fall 2021 Edition), Edward N. Zalta (ed.), forthcoming URL = <https://plato.stanford.edu/archives/fall2021/entries/value-theory/>.