Faith in the Intelligibility of Being - A Response to Humean Skepticism
So I am currently reading from Peter Kreeft's book Socratic Logic: A Logic Text Using Socratic Method, Platonic Questions, and Aristotelian Principles and in the Introductory chapter Kreeft brings up the point that Aristotelian logic depends on an "epistemological realism," which the epistemologies of David Hume and Immanuel Kant cannot provide. Kreeft defines epistemological realism as: "...the belief that the object of human reason, when reason is working naturally and rightly, is objective reality as it really is." Kreeft's reflection on Hume reminded me of my reading of Hume's Essay Concerning Human Understanding last Summer. Humean skepticism has probably been one of the more difficult skepticisms to refute that I have run into. I have even heard this skepticism wielded by the Physicist Sean Carroll on his podcast Mindscape. He recorded an episode which took up the question, "Why is there anything at all?" and in which he used Hume's skepticism to say that there is no answer. Carroll, whose whole career is based on uncovering the cause-effect structure of the scientific discipline of Physics, says that when we get to questions regarding the cause of the universe or of an event like the Big Bang that maybe "there just is no cause," that causality no longer is necessary or applies. Needless to say he is an atheist and admitted that his answer is based on Hume's skepticism towards causality.
Truth as Essences
To understand Hume's Skepticism it would be helpful to first refer to Plato and one of Plato's fundamental discoveries about philosophy. What set Socrates and Plato apart from the PreSocratic explanations about the nature of being, and its change and stability, was the realization that human knowledge is fundamentally universal and essential in character, while the material reality was singular and individual. The PreSocratics had rightly identified that there are two fundamental realities about nature that have to be explained, that of the changes that go on all around us all the time and yet the stability that remains in things despite those changes. The Heraclitan river is a fine example, it is always changing yet it is still the same river which persists over time. Plato realized that while the material reality all around us changes, it is our thoughts about it that seem to be the source of stability in things. The idea of "river-ness" is something that is unchanging and eternal, while the physical river undergoes many changes in time. All ideas have a nature to them which seems to take on a new type of being. They embody the universal characteristics of things and function as a type of "form" or template of the material world around us. Thus they must exist on a higher plane, and because they are unchanging in this form, must be more real than their physical examples. Truth then is remembering (or uncovering) the eternal realities which physical things represent. Aristotle will shift things around to say that these eternal forms are not in a higher realm, but exist as the non-material grounding or "substance" in all things which undergirds the physical representation that undergoes changes. Truth is the abstraction of the eternal forms present in the physical things by the mind.
With this in mind, let's shift to Hume now. Hume's skepticism runs something like this. Hume does not necessarily believe in substantial forms like Aristotle, and is a reductionist, but in so many words, Hume's skepticism hits upon the fact that the "essences" in things are not known directly, but only indirectly known through their individual and material instantiations by our five senses. Therefore, I only know the essences by abstracting the universal with the mind from each particular that I encounter. In a sense, I am having to piece together the full and complete picture of the universal over time as I come to understand all the different facets of that type of thing. But since I don't know the essence directly and completely, but only piece by piece in a mediated way, Hume claims that true knowledge of the essence of a thing in the world is impossible. Since the universal is known through the particular there could always potentially be a new individual who fundamentally upsets everything that is known about that type of things or essence. Thus, Hume claims that deductive certainty about essences known from our experience of the world is impossible, we can only have probability. This too holds for the fundamental and universal laws of being that are known through experience, like cause and effect. Since we cannot know the essence of the law of cause and effect in itself but only put it together in our minds from the individual examples of cause and effect we see, it cannot be a law with absolute certainty. Hume holds that there could always possibly be an example where the law breaks down in the future. The only exception to this for Hume is the knowledge that comes from our perceptual or rational structures in the mind. Geometry is an easy example to take. He is okay with saying that a triangle has three sides has deductive or necessary certainty because those essences are present within human perception and could not ever be otherwise.
In a way, Hume is the anti-Plato in that if Plato exalted the being of essences and the mind to be an eternal and necessary realm, Hume exalted the particularity and limitations of the senses to bring humanity down towards a skepticism of higher things.
What the is the proper Aristotelian response to Hume? While Hume is right that essences are mediated through our knowledge of the particular, there seem to be some essences that are so universally true and self-evident that one cannot deny them without destroying all knowledge and perception whatsoever. Both the principle of non-contradiction and the principle of causality are like this. They are the most fundamental laws of human perception of the world. To deny them would not only do what Hume wanted them to do, undermine our trust in the coming to know essences of things, but also undermine perception and human subjectivity itself. The person's experience of their own thoughts and perceptions in their subjectivity is still predicated upon the idea that being is not contradictory of itself (PNC) and that being is coherent (causality). Otherwise perception would not make sense, thoughts would not make sense, neither ideas or language, neither Hume's argument itself for skepticism. Hume is assuming the truth of these fundamental laws of being to try to refute them. So there are only really two options left.
One option is to fall into a complete skepticism even of one's own perceptions and thoughts and remain as a "vegetable." Even if one said even perceptions are only subject to probability and nothing has deductive certainty, one could have no certainty regarding that, nor what the idea of probability even is, or that probability is a reality that should be trusted to be consistent. Likewise how does one know if the causal connections that one witnesses in their perceptions are true? Or that probability is a causally valid idea to describe them? In the end, either these self-evident truths of experience and reality must be trusted or the whole system collapses.
The other options is to have a natural faith and accept the self-evident truths of the intelligibility of being. Being is consistent with itself in its existence and interactions with itself. To add to this, if essences, as Aristotle thought, can be proven to exist, then logically if being is consistent with itself, those essences, being universal, would be consistent and in knowing one of them you would know the rest.
Epistemological Realism is the only way to perceive, think, and act in the world. Aristotle's epistemology of realism seems to be the only way to NOT fall into a complete skepticism regarding truth, while Hume's skepticism toward knowledge of essences fails to apply its implications to the rest of his system but only to those parts of truth which he did not like in that they directed the human mind to the knowledge of God's existence.