When, for example, we have the idea or concept of "tree," we...

When, for example, we have the idea or concept of "tree," we have knowledge of what tree means; we can write the definition of tree as such; the definition is applicable to each and every possible tree, regardless of size, location, botanical class. For, we know an essence, and we know it as abstracted from the circumstances and limitations that mark the individual things which have that essence in the world of things outside the mind.

This is what we mean by saying that ideas are universal ideas, and that we know things in universal. Now, there is no question that the thing known in an idea or concept is present to the mind in an abstract and universal way. But there can be question about the way in which that…