I argued in Part I of this discussion that the Argument from Disagreement (AfD) draws its strength from the ignorance of the listener. The history of philosophy, on superficial inspection, seems to present itself as a never-ending series of disagreements that are never really resolved. Ignorant of the substance of those disagreements, the listener assumes them to be fundamental to philosophy and to characterize its essence. But disagreements are only meaningful if they are knowledgeable, and to know if they are knowledgeable, we must understand philosophy rather than dismiss it with a priori arguments. Continuing that theme, I will argue here that disagreement can’t possibly be the essence of philosophy.
Disagreement is only possible in terms of a more fundamental, underlying agreement between the parties involved. If philosophers are in utter disagreement with each other, they can have nothing to say to each other, for they will have no place from which to begin the conversation. But there is no point in endlessly repeating points of agreement. The conversation is only advanced when we address points of disagreement and see whether they can be overcome. Therefore it is natural that philosophical dialog would seem, to the superficial observer, to be characterized primarily by disagreement. For even if philosophers largely agree with each other, they will not spend their time reciting their agreements but rather hashing out their disagreements. The long history of philosophical conversation, including its disagreements, is testimony to what can be known through philosophy, not the fruitlessness of philosophy. If philosophy were the vain endeavor its critics suppose it to be, then men would have long since stopped indulging in it.
Let us take a specific case to flesh this point out. An ancient and fundamental philosophical question concerns the one and the many, or unity and multiplicity. The question arises because philosophers long ago recognized that unity is not just another thing we know about or experience in the world; it is in some sense behind everything we experience in the world. I wake up in the morning and see the sun and know that a new day has begun. The sun comes to me as a combination of unity and multiplicity. Its rays come to me over time and I can see that the sun is spread out in space. In that sense, I can see that the sun is multiple because it is divisible in time and space. On the other hand, it is one and the same sun that I experience across time and that is spread out across space. In that sense, I can see that the sun is a unity. What is the relationship between unity and multiplicity in the sun, and what is it about the sun that allows it to be both unified and multiple? Furthermore, I see that these same notions of unity and multiplicity characterize other things in my experience, from dogs and cats to trees, boats and rocks, to the number “five” and my own self-identity, to law and the meaning of justice (Is there one justice that men know or are there many different justices that go by the same name?) In fact, unity and multiplicity characterize everything in my experience to such a degree that we may wonder if it is possible to have any experience at all without having an implicit experience of unity and multiplicity. Unity and multiplicity are not ordinary attributes like color, size, shape, evenness, or number. These latter attributes can be applied to some things and not others. An apple has a color but it is neither odd nor even; the number five is odd but does not have a color. But apples, color, evenness, and five all participate in unity and multiplicity. Unity and multiplicity are what may be called “transcendentals” because they transcend all other attributes in the sense of being more fundamental than any of them. Philosophers, whose deepest desire is to get to the most fundamental truth about things, naturally home in on the transcendentals as a point of conversation.
All that I have written in the last paragraph is a statement of near universal agreement among the philosophers of history. The problem of the “one and the many” was first clearly stated by Plato, and he framed the conversation as it continued in Aristotle, Plotinus, Thomas Aquinas, Leibniz and Kant, among many others. Understanding the difference between transcendentals and ordinary attributes was a prerequisite to joining the conversation and constituted the basis of agreement on which the conversation was conducted. (This is why Plato is indispensable basic reading in philosophy.) But, of course, philosophers did not spend the bulk of their time congratulating themselves on their mutual agreement. They spent their time discussing their different answers to the question of the ultimate nature of the one and the many.
The difference between Thomas Aquinas and Kant, for example, may be understood in terms of the different answers they give to the question of the one and the many. For
I side with Aristotle and