  The reasoning to the first conclusion is straightforward. By P4, knowledge is what it is in relation to what it is knowledge of. Consequently, by P3K, if X is knowledge in humans, then the object of X (i.e., what X is knowledge of) is in humans. Now, according to Separation, every form is itself by itself. But, by P1, nothing that is itself by itself is in humans. Consequently, whatever is in humans is not a form. So if X is knowledge in humans, then the object of X is not a form. That is to say, no knowledge in humans (i.e., no knowledge that humans have) has any form as its object.  Thus, from Separation, P1, P3K, and P4, it follows that humans do not know any forms.