The second [premise] is their assertion that every contingent existent possesses, outside the mind, a quiddity that is its very essence and reality—distinct from the concrete, particular existent that is known and established in the external world. Here again they have confused what is in the mind with what is outside it.

For if by “quiddity” one intends that which is conceived in the intellect—the answer to the question, “What is it?”—and by “existence” that which is objectively realized outside the mind, then it is plain that the one is not the other.

They themselves say: “We can picture a triangle before we know of its existence in the external world.” From this they conclude that the quiddity of the triangle is other than the triangle that exists outside the mind.

Say to them: If you merely mean that the triangle conceived mentally is different from the triangle that exists in reality, that is true. Yet nothing in this entails that, outside the mind, there are two things:
• first, the quiddity of the triangle, which is its essence and reality; and
• second, the existent triangle that forms, for instance, the corner of a wall.

If, however, you maintain that there are two distinct entities outside the mind, you are mistaken. This very point has bewildered many investigators; some of their leading figures have been reduced to hesitation and suspension of judgment. Others vacillate and contradict themselves, and the cause of it all is their failure to distinguish between what is conceived in the intellects and what is found in concrete reality.

And this topic—