The hasan li-ghayrihi hadith and the hasan li-dhatihi hadith?

The Shaykh : The science of hadith is not merely in its rules, but also in the depths of its days; it is like this knowledge which has fixed rules, many of which are fixed with final precision. If a reader were to say, "Ahmad hit Muhammad," the scholars in this science would agree to correct him. However, this is not the case with the subtle sciences of hadith, such as the science of the hasan li-ghayrihi hadith, and indeed the hasan li-dhatihi hadith. I have spent, and I have spent, nearly half a century of time, and usually I say more than half a century, but regarding the following issue, it is not permissible for me to say: "I have spent half a century or more." Rather, I said—and I mean what I say—that I have spent less than, or close to, half a century studying this science. This was not merely theoretical, for studying it theoretically is easy and requires only a few years if the student has been given talents, free time, and similar aids to enable him to master this theoretical science. What I spent and mentioned regarding the study of this science was practical. Before I reached half a century in studying this science, I came across a manuscript in the al-Zahiriyyah Library by al-Hafiz al-Dhahabi: a very pleasant treatise that was printed in our recent times, titled "al-Muwakkizah." During that period that has passed for me—which is less than half a century—and while I was studying, the reality became clear to me, which al-Hafiz al-Dhahabi expressed in that treatise. I was greatly pleased by that teaching because it agreed with what was in my heart: that the hasan hadith is among the most subtle sciences of hadith. Why? Because al-Hafiz al-Dhahabi (may Allah have mercy on him) mentioned in this treatise the meaning I had felt throughout that period. He said: "The hasan hadith is among the subtleties of the science of hadith." Why? Because the opinion of a single hadith scholar differs regarding this hadith; sometimes he grades it as hasan and sometimes he weakens it, and he is one person. So what can be said if this observation moves to two people who differ in understanding, knowledge, and age? The matter will be more subtle than what al-Hafiz al-Dhahabi mentioned in his treatise "al-Muwakkizah."
And more subtle than this is the hasan li-ghayrihi hadith. One may find, as in this example before you, that the first route is an addition to the other route, and it may not seem to him in itself that it is a hasan hadith. But when he sees that this hadith came in the interpretation of that noble verse, and that the verse does not admit of many meanings, but rather means exactly what came in this hadith, then it dawns in the mind of this researcher that this hadith, by the first route and the other route, and the addition, is the meaning guaranteed in the verse. At that point, it dawns in his mind that it is a hasan hadith. If another person comes and critiques it with a personal critique, saying: "This is a weak hadith," not because the first route has such a defect and the other route has... before its time, this does not mean that he has brought something that establishes the argument against the one who graded it as hasan. Rather, perhaps the opposite is correct. Therefore, I said at the outset that in such an issue, we may not reach a point where we put forward a definitive opinion. Because I observe in the many observations that come to me from some of those engaged in this science of hadith—some send me their letters, and some rush to print and publish—I observe that these and those have some following of the terminology or biographies of the men, but they have not been kneaded with this science by applying it practically. And so they fall into much of what can be said at least is that there is no benefit in the research, because it will not bring anything new to the critic except in some cases. We observe some of this with our own selves, and they observe some of it. For example, if I say in a hadith in one book: "This is hasan," and I say in another book: "It is weak," then this contradiction is undoubtedly an apparent matter that requires preferring one of the two grades. As for someone setting himself up to bring what is not hidden from... as is this, he should ask himself: WhyThe Shaykh : do you think he graded this hadith as hasan while the weakness is clear in both routes? They never mention such an observation as al-Imam al-Dhahabi mentioned in "al-Muwakkizah." And this is what opens the circle of discussion in something that is not beneficial.
This is what comes to my mind in answer to this question.