If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, "Does it contain any abstract reasoning concerning quantity or number?" No. "Does it contain any experimental reasoning concerning matter of fact and existence?" No. Commit it then to the flames: for it can contain nothing but sophistry and illusion.
While logical positivism as an organized philosophy has died out, there still remain many who, along with Hume, would affirm a death sentence to metaphysics. This contemporary school of thought still takes metaphysics as essentially ambiguous and superfluous.
I myself, as a Scholastic, would disagree with this. The Scholastics—a school of philosophy which is actually increasing in adherents—would claim that not only should metaphysics be utilized, but that it must. It would be claimed by them that metaphysical concepts like identity, essence, form, substance, and act/potency etc., describe fundamental properties of reality, and therefore that such concepts are necessary for a sound framework regarding the nature of reality in the first place.
However, the contemporary positivist scoffs at such assertions. They would claim that concepts like the ones mentioned above are, even if remotely accurate—of which the positivist would most likely claim they are not—completely superfluous for describing reality. Physics already tells us how one event can, and does, follow another, and thus the need for a description riddled with the act/potency distinction is not necessary. Likewise, physics and chemistry already enlighten us regarding what physically composes and makes up a certain empirical object, so that to add descriptive concepts like identity and essence on top of these physical explanations and descriptions is to upset the principle of parsimony. Science, it is seen by contemporary positivists, already tells us (or will eventually tell us) all we need to know about the objects and phenomena that make up our observable universe. Hence, the need for any metaphysical description is seen as completely superfluous.
While such a position might seem rational, especially since science has been extremely successful in a pragmatic and predictive sense, I maintain that said position is not only false, but demonstrably so--and for multiple reasons at that. First, the picture that science provides of the material world can only be seen as comprehensively descriptive if one assumes ahead of time that reality can only be described in scientific terms and concepts. Theologian David Bentley Hart, in his amazing book The Experience of God, articulates such fallacious thinking:
And naturalism’s claim that, by confining itself to purely material explanations for all things, it adheres to the only sure path of verifiable knowledge is nothing but a feat of sublimely circular thinking: physics explains everything, which we know because anything physics cannot explain does not exist, which we know because whatever exists must be explicable by physics, which we know because physics explains everything. (p. 77)
The problem here should be obvious. Moreover, the claim that science gives us an exhaustive portrait of reality is itself a claim that only metaphysics, and not science, can make. So, even ignoring the question begging nature of positivism alluded to above, the positivist still has the problem of utilizing the very method they’re attempting to overthrow. They’re basically claiming the following: all metaphysics is meaningless, except for the metaphysical statement I’m making currently.
The second problem that positivism runs into—as if being subject to question-begging and self-refutation weren’t bad enough—is that the scientific method already a priori rules out the kinds of descriptions that could be considered metaphysical in the first place. You see, the objective of science was to be able to control and predict the world around us using the language of mathematics. This means, and this is crucial here, that science is, already at the outset, only looking for a quantitative description of reality—thereby paying no attention to anything qualitative or metaphysical. This is to say, the scientific method already stipulates what kind of answers and descriptions it’s looking for. It’s not as if science, looking for the quantitative, will somehow stumble upon the metaphysical, because it’s not looking for the metaphysical. To use an example, science will not stumble upon the ‘essence’ of a substance, because science is not looking for ‘essences’ in the first place--precisely because a thing’s essence cannot be modeled by the language of mathematics and prediction. Philosopher Edward Feser, in his (also) amazing book Scholastic Metaphysics, further articulates my point:
The reason qualitative features don’t show up is not that the method has allowed us to discover that they aren’t there but rather that the method has essentially stipulated that they be left out of the description whether they are there or not. (p. 14)
And again, David Bentley Hart reinforces the point:
If we look exclusively for material and efficient processes, then indeed we find them, precisely where everyone, of nearly any metaphysical persuasion, expects them to be found. All this shows is that we can coherently describe physical events in mechanical terms, at least for certain limited practical purposes; it certaintly does not prove that they cannot also be described otherwise with as much or more accuracy. To paraphrase Heisenberg, the sorts of answers that nature provides are determined by the sorts of questions we pose of her. (p.65)
Moreover, there is a third problem for positivism. You see, science, and physics most importantly, only enlightens us regarding how nature tends to behave, or how certain events produce or tend to be produced by others. Atheist Bertrand Russell articulates:
[Physics] lays down certain fundamental equations which enable it to deal with the logical structure of events, while leaving it completely unknown what is the intrinsic character of the events that have the structure[…] All that physics gives us is certain equations giving abstract properties of their changes. But as to what it is that changes, and what it changes from and to—as to this, physics is silent.
Now, the reader might be inclined to part ways with Russell here. “Surely” one might claim, “physics does tell us the intrinsic nature of things. Physics give us comprehensive knowledge of the physical characteristics of certain objects, and describes how it is possible for these objects to behave the way they do.” But this is only half true. No matter what explanations and descriptions that physics gives of certain characteristics of an object or event, these descriptions themselves will still only boil down to abstract mathematical equations and functions. For example, for physics to describe the behavior of object (x), physics will posit the description that A events follow B events, of which object (x) is a part of. But, A events and B events will also only be subject to further descriptions of certain other objects following certain other sequential events. So, no matter how many layers of physics one traverses to explain a certain object or event, one will invariably run into nothing but abstract behavioral descriptions dancing to the tune of mathematics—and this, again, only gives structure, and does not enlighten us regarding any sort of intrinsic nature that these objects or events have themselves. I’ll pass the baton once more to Feser:
By the very fact that physics tells us that an abstract structure of such-and-such a mathematically describable character exists, then, physics implies that there is more to reality than structure itself, and thus more to reality than what physics can reveal. (p.18)
These three problems (there are others) articulated above suffice to show that positivism is, quite frankly, vacuous. Nowhere have we uncovered any cogent reason to believe that metaphysical descriptions are superfluous, nor have we seen any reason to believe that science gives an exhaustive description of reality. On the contrary, we’ve seen that metaphysical explanations and concepts are completely necessary, and are required, even in light of, and because of, science. Metaphysics, then, is here to stay. Thus stated, we shouldn’t be worried about utilizing metaphysical inquiry, but rather we should be worried about utilizing it fallaciously, and I think the positivist position is a good example of how this can be done.