When we see multiple dogs in a yard, we know that each is a different dog, but also that all the dogs are the same in that they’re all dogs. The sameness between them is the universal, which may be called “dogness”.
I had thought that “dogness” was basically the “picture” that you have in your mind of that which all dogs have in common. But something someone said today caused me to realize that a universal can’t be pictured at all.
When you try to picture dogness in your mind, in fact what you are picturing is a particular dog. This is because you can only picture a dog of a certain size, shape, color, and with a particular dog face. You can change the image if you want to, from brown to black to golden fur, etc. But you can only imagine it one way at a time. Thus, whatever image you are holding in your mind at a given moment, is of a particular dog.
Therefore, you can only imagine a particular dog, and not “dogness” per se.
Before this realization, I knew that I knew what dogness was, even without putting it into words, and therefore knew that it wasn’t a verbal definition. And since it wasn’t a verbal thing, I assumed it was a mental picture. But now I realize it’s not that either.
You can draw verbal descriptions from your idea of dogness: Dogs have four legs, they have fur, they tend to behave in certain ways that other animals don’t. But my idea of “dogness” doesn’t consist of those words.
The New Advent Catholic Encyclopedia states of the intellect that its function “is to divest the object presented by sense of its material and individualizing conditions, and apprehend the universal and intelligible form embodied in the concrete physical reality. The outcome of the process is the generalization in the intellect of an intellectual form or representation of the intelligible being of the object (eidos, noeton). This act constitutes the intellect cognizant of the object in its universal nature.”
In other words, our minds strip away the physical aspects of the thing, say, the particular qualities of the individual dog we’re looking at (size, color, etc.), in order to form a general idea of “what” the thing is, which is applicable not only to this dog but to all dogs. But the general idea is not a picture. Rather, it’s an idea. St. Thomas Aquinas refers to this as the intelligible form of a thing, and we do it with everything we encounter. The thing about the dog which is left over after removing the particular qualities of this particular dog, is what makes the dog intelligible; in other words, makes it capable of being received into our intellect.
Another way of putting it is, that we strip away the material and what’s left is the immaterial and therefore non-picturable. It is in this way that we come to know that we possess an intellect, and that it is of an immaterial nature. As St. Thomas writes, “it is manifest that by knowing the intelligible object it understands also its own act of understanding, and by this act knows the intellectual faculty”. ST I-I, Q. 14, A. 2.
This also, according to St. Thomas, relates to how we come to know God himself. But that’s another story…