The thing about Leonard Nelson that I think is a bit off putting to people is that his approach of non intuitive immediate knowledge is thought to be a species of psychologism. That is that truths of logic or science depend on the human mind. Well Dr. Kelley Ross shows that that is not what Nelson was saying at all. But Husserl attacks that problem head on. He brings three proofs against it.[in the first part of Logische Untersuchungen. Erster Teil: Prolegomena zur reinen Logik (Logical Investigations, Vol. 1)]
The thing that I noticed is Husserl's proof depends on there being absolute truth. That is, that there are truths that do not depend on the observer. And the best proof of that from what I have seen is John Searle's. Searle shows that if all truth is relative it sinks into there being no truth at all by means of "dis-quotation." That is the "sentence snow is white", only if snow is white. (And snow is white is true only if it is true with respect to a background in which things can be white or not white.) It is a short proof. [It is good that Searle was attacked, since nowadays when universities attack someone, it just shows the greatness of that person.]
I noticed there is a new Kant-Friesian on the horizon- Michael Cuffaro.