The Austrian philosopher Alexius Meinong formulated a wide-ranging metaphysical/semantic theory which is intended to address many issues of fundamental importance; particularly issues to do with existence, reference, and intentionality. His theory affirmed a number of theses, some which had antecedents in the history of philosophy, and others which were truly radical. Some of the central theses are:
Every thought has an object which is the target of that thought.
Objects need not exist.
We can make true claims about nonexistent objects.
An object possesses its characterizing properties irrespective of whether it exists.
Indeed, Meinong's theory contains a number of other distinctive theses, but these are the most important for our purposes here.
In his well-known criticism of Meinong's theory, Bertrand Russell claimed that Meinong lacked a "robust sense of reality". Russell here was drawing upon an old idea that goes all the way back to Parmenides. Put simply, Parmenides claimed that for any true statement we make, the objects which that sentence are about must actually exist. 2 corollaries of this claim are that an object can possess properties only if it is actually existent, and therefore all objects are actual existent objects. Parmenides recognized this fact and did not shirk from making these affirmations.
In the modern guise, these Parmenidean theses give rise to the logical inference known as Existential Generalization (EG). To put it in brief, EG says the following:
If we have a true sentence about an object x, then we can conclude that x actually exists.
In Parmenides' theory and the classical logic which derives from it, EG is universally valid. But it is not so for Meinong's theory. Indeed, for Meinong we can only ever conclude that an object x exists if we have premise which asserts the actual existence of x.
Russell, and the Parmenidean tradition he is drawing upon, is appealing to an understanding of philosophy which goes back to the very beginnings of the subject; namely that philosophy must deal with what is really real. And indeed, it seems we can only do that by focusing our sights on actual existence
Now with regard to Russell's charge against him, Meinong replied in an equally dismissive manner by accusing Russell of displaying a "prejudice in favor of the actual". For Meinong, it was just obvious that not every object is an actually existent object, and therefore that EG is not universally valid.
Meinong just like Russell is also drawing upon a time-honored conception of philosophy, which is the notion that philosophy must be absolutely unrestricted in it's application. In effect, no stone must be unturned. Or to put it differently, no object must be off-limits to philosophical analysis. Both of these ideas, viz. that philosophy must be fundamentally concerned with actual existence and that it must not limit the objects to which it can be applied, seem very sensible. But it would appear that they are fundamentally in tension with one another.
As far as the contemporary debate goes, we find ourselves in much the same scenario, with seemingly little hope of finding a way out. But in this post I would like to explore an alternative route we might take; one which is rooted in the work of the medievals. For I think medieval logic affords us a possible middle road between the Russellian and the Meinongian positions, and this might allow the 2 camps to find some common ground.
But before we begin, we need to briefly cover some important points from medieval logical theory.
In medieval logic, every proposition (i.e. declarative sentence) is composed of 2 terms linked together by a copula. Oversimplifying a bit, a term is a word or phrase which refers to something outside of itself. Take the familiar proposition: Socrates is mortal. Here the two terms are "Socrates" & "mortal", while the copula is the word "is".
We mentioned how terms refer to something outside of themselves. For the medievals, it was not always strictly determined just what it was that a term referred to. This could change depending upon the proposition it was a part of. And here the medievals came up with a new word, i.e. 'supposition'. Put briefly, supposition is a property of terms which determines the objects to which they refer within the context of a proposition.
Let's consider an example. Imagine we have the following propositions:
A. Man is a rational animal
B. "Man" is three-lettered.
These propositions both share a common term; namely, 'man'. But upon inspection, it is clear that 'man' in A refers to something very different than what it refers to in B. And thus we say that in A 'man' supposits for the species Homo Sapiens; but in B 'man' supposits for an English word. The other terms in the proposition allow us to determine the object to which the term supposits; for only a species is the kind of object which can be a rational animal. Likewise, only a word is the type of object which can have three letters. Indeed, the familiar notion from grammar school of context clues if helpful here. For if we are unsure which object a term refers to in a proposition, we need only use the clues provided by the rest of the proposition to answer that question.
Now as we can see, the terms in both A and B are linked together by an "is" copula, and this is important. For in medieval logic if we have a proposition in which both terms are linked together by a simple 'is'-copula, then such a proposition can only be true if both terms supposit for actually existing objects. Or to put it more explicitly:
"For any proposition of the form 'X is Y', both X and Y must be actually existing objects if the proposition is to be true."
At first glance it seems as if the medieval logician agrees with Russell, and he is just merely using some novel terminology. But this is not true, for there is another important facet of medieval logical theory; and that is the notion of ampliation. Put simply, ampliation is a process whereby the supposition of terms is expanded in some way or other. Consider the following proposition:
C. Wooly mammoths were mammals
Clearly C is true, but not because wooly mammoths are actually existing objects. For they are long extinct, and thus they no longer exist. So how can this proposition be true? It is precisely the notion of ampliation which explains how.
Let's analyze the proposition to see how it works. As before, we have 2 terms; this time they are 'wooly mammoths' and 'mortal'. But now we have a new copula, viz. 'were'. This is the crucial difference; for this new copula is telling us that the terms of the proposition can now supposit for not only what actually exists, but also for what did exist in the past. Thus, 'wooly mammoths', as it occurs in C, supposits not for actually existing wooly mammoths (of which there aren't any), but for wooly mammoths that existed in the past.
That is precisely what ampliation does: it expands the objects for which a term can supposit in a proposition. Can ampliation be pushed further? Yes indeed, for consider this proposition:
D. Space elevators will be useful tools.
Suppose D is true. This clearly cannot be the case because of any present or past space elevators. Such things do not currently and have never yet existed. Rather, it is true because of the space elevators that will exist in the future. As expected, it is the "will be" copula which is doing the work here. For this new copula ampliates the supposition of the term 'space elevators' to include not only presently and past existing space elevators (of which there aren't any), but also to future space elevators.
We've covered a lot of ground already, but let's push further. Consider now this proposition:
E. Dragons can be larger than elephants.
E seems perfectly true. But dragons never have, do not currently, and plausibly never will exist. Nevertheless though, dragons could possibly have existed, and that is precisely the key here. For the 'can be' copula ampliates the supposition of the term to include not only present, past, and future dragons (again, of which there aren't any), but also to dragons which could possibly have existed.
Now for most of the medievals, this was as far as they were willing to go. In their eyes, terms in a proposition could only supposit for things that are, were, will be, or can be. But a few radicals went even further. For these logicians, terms could potentially supposit for objects which could not possibly exist.
A favorite example used in this context is a chimera. Today we imagine a chimera to be a type of creature with a lion's head, a goat's body, and a snake's tail. But the medievals had supposed chimeras to be a type of creature which is at one and the same time a lion, a goat, and snake. Clearly, it is impossible for such a creature to exist. Nevertheless, consider the following proposition:
F. Chimeras are imagined to be monstrous creatures.
That seems perfectly true, but chimeras are necessarily nonexistent. Thus, it would appear that the "are imagined to be" copula allows terms to supposit for impossible objects. Indeed, the few medievals who went this far considered such couplae as "is imagined to be", "is conceived to be", "is understood to be", etc., to similarly allow for terms to supposit for impossible objects.
So now that we understand all of that, how does it apply to the dispute between Russell and Meinong? Well, let's consider what each of them would have said about supposition.
To do this, let us construct a list of copulae:
3. "will be"
4. "can be", "could be", "may be", etc.
5. "is imagined to be", "is conceived to be", "is understood to be", etc.
(As a reminder, most medievals would not have recognized type-5 propositions as their own category, and would have instead just subsumed them under type-4 propositions. But we will include this more radical medieval view because it makes it much easier to accommodate Meinong's position).
And let us call a proposition with an "is"-copula a type-1 proposition. And one with a "was"-copula will be called a type-2 proposition; and so on down the line. Assuming that Russell would be comfortable with speaking of supposition (a dubious assumption indeed, but let us make it anyway), what would he say about the supposition of the terms in any given type of proposition? The answer should be clear: he would affirm that the terms for propositions of any of the 5 types must supposit only for actually existing objects. Indeed, that is in fact just a restatement of the rule EG, using medieval logical terminology.
But what would Meinong say? His view is just a radical as Russell's, but from the opposite extreme; for Meinong would say that the terms in any type of proposition can supposit for any type of object whatsoever. So what this means is that no matter what type of proposition we are considering (even type-1 propositions), its terms could potentially supposit for all sorts of nonexistent and indeed even impossible objects.
As we have seen already, the medievals erected a middle ground between these two extremes. For they believed that the terms in different types of propositions supposit for different types of objects. Let us lay their view out in tabular form like so:
Type-1 --> what is
Type-2 --> what is or what was
Type-3 --> what is, what was, or what will be
Type-4 --> what is, what was, what will be, or what can be
Type-5 --> what is, what was, what will be, what can be, or what cannot be
It should be clear now: where both Russell and Meinong don't discriminate among any kind of proposition, the medievals make subtle distinctions between cases. And it would also appear that the medieval's approach to this question is far more commensensical. For it would appear quite improper to arbitrarily restrict all 5 types of propositions to only actual objects; and yet, it might also appear too careless to allow for any kind of proposition, even those of type-1, to apply to even impossible objects. The medieval's view can waylay both of these worries.
And now we can see how the problem mentioned earlier (viz. how can we reconcile the view that philosophy must be concerned with actual existence with the view that philosophy must not limit the objects to which it can be applied) can be resolved. For when philosophers deal with the fundamental nature of the world they will spend most of their time dealing with type-1 propositions, and these, according to the medievals, deal only with actual existence (which satisfies what the Russellians are after). But when philosophers are dealing with questions regarding the limits of the world, the bounds of possibility, or the objects of human thought, they will need to employ propositions of types 2-5. And in these cases they will be dealing with broader classes of objects, up to and including those which could never exist (and thus satisfying the desire of the Meinongians).
So in closing, I should like to say 2 things: firstly, if we limit ourselves to the machinery of contemporary symbolic logics (whether they be classical or non-classical), the Russellian and the Meinongian will always be at loggerheads. But if we appeal to the technical machinery provided by medieval logic, then they can truly find some common ground. Secondly, I hope to have provided a glimpse of how useful the work of the medievals can be in illuminating contemporary problems in logical theory. I sincerely hopes this inspires more people to discover for themselves the marvelous riches of medieval logic.