Ok, you don’t accept St. Thomas’ idea that all that is in our intellect arises from our sense experience. You need the Leibnizian observation to be added that the intellect itself does not arise from our senses.
How must this famous observation be understood?
St. Thomas never said that our intellect arises from our senses; so, it seems there is no disagreement in this point between Leibniz and him. But St. Thomas thought that our intellect did not have any form by itself, but that it could take any form. The intellect was in potency to receive any form. So, for him, every form that the intellect was able to take had to exist before the cognitive act, and for the cognitive act to take place an experience was needed. So, all our knowledge was “a posteriori” for him. But Augustinian Dr. Nash, who apparently rejects Platonism (though Roman Catholic St. Augustine followed and loved pagan Plato), thinks we have some “a priori” knowledge; that is to say, we have innate ideas or forms in our intellect. However, he remarks that those innate ideas are not explicit or conscious at birth, but only implicit. What is necessary for those ideas to become explicit or conscious? Experience! And he says that an example of those innate ideas is “equality or similarity”. So, you have in your mind the knowledge of equality, though you don’t know you have it. You need an experience for you to know that you know it. What experience is it? Can it be any experience? Dr. Nash says that there are some people in the United States that due to the “education” they receive in the school will never be conscious of their innate ideas. I guess he knows he is exaggerating, but the point is that he thinks that it is not any experience which will be the occasion for the awareness of your idea of equality: it has to be a very specific experience. There must be a peculiarity in such experience that is able to make your idea of equality explicit. But what can this peculiarity be if it is not equality itself? At least that is what an “empiricist” like Roman Catholic St. Thomas (follower of pagan Aristotle) would say.
So, it turns out that both humble rationalist reformer Dr. Nash and Roman Catholic Thomas say is that for you to know equality you need an experience of equality.
On the other hand, according to Dr. Nash, it is false that “no knowledge at all arises from our senses”. He is humble and, therefore, he admits that there is some knowledge that arises from sense experience. What do you need to acquire one of those knowledges? Experience, obviously! But which experience can it be? Can it be any experience? Of course not! It has to be a very specific experience too! There must be a peculiarity in such experience that is able to actualize your intellect with a certain form (that is at least what Thomas would say). Humble rationalist Dr. Nash has to admit it (unless he has another reason or unless he is not so rational, or unless he is not so humble).
So, it seems that whatever the knowledge we are talking about, there is a specific kind of experience which is required for your intellect to become actualized: You don’t have it? Then your intellect is not actualized.
Then, what is the difference between the “empiricist” and the rationalist? The difference is that the rationalist will say “no, but some of those knowledges were already in the intellect, though implicitly?” But what are the reasons of the rationalist to say that (especially for those humble rationalists who reject Plato’s reasons)? And how does he discern between those knowledges that arise from sense experience and those which do not?