In a letter to Feuerbach, Marx in 1843 wrote
How cunningly Herr von Schelling enticed the French, first of all the weak, eclectic [Victor] Cousin, then even the gifted Leroux. For Pierre Leroux and his like still regard Schelling as the man who replaced transcendental idealism by rational realism, abstract thought by thought with flesh and blood, specialised philosophy by world philosophy! To the French romantics and mystics he cries: "I, the union of philosophy and theology," to the French materialists: "I, the union of flesh and idea," to the French skeptics: "I, the destroyer of dogmatism," in a word, "I ... Schelling!"When you first read this, you'd swear it was something from Nietzsche's nachlass. Suddenly you realize that all that shrewd poison and psychologizing was more or less just in the air in the latter half of the 19th century. This was one of the accepted and expected ways to think, and if you were an intellectual in that milieu, you picked it up and got good at it. (Of course, not everyone got as good at it as Nietzsche.)
Schelling has not only been able to unite philosophy and theology, but philosophy and diplomacy too. He has turned philosophy into a general diplomatic science, into a diplomacy for all occasions. Thus an attack on Schelling is indirectly an attack on our entire policy, and especially on Prussian policy. Schelling's philosophy is Prussian policy sub specie philosophiae.
This is one of the nuances (and no less crucial for being a nuance) that is lost when you read philosophers of the past out of context, as documents in a line of "arguments" about such-and-such a subject.
This could easily be mis-read as an argument for incorrigible historicism, or at the least that one requires a host of footnotes or some kind of sensitive antennae in order to "really read" thinkers of the past. A certain kind of impatient student is rightly suspicious of such implications. "Why should I care about the "historical context," they want to know. "Just give me the arguments." There is a certain prima facie plausibility to this objection, for surely, as Aquinas argued (and I have cited it before), "Philosophy does not consist in asking what men have said, but in asking after the truth of the matter." This argument looks like it is saying, "cut to the chase," or, more generously, it doesn't matter when and who said it and in what set of cultural assumptions, what matters is, is it true, or slightly more broadly, is it a good argument?
But when you read a thinker -- and it needn't be someone shelved in the philosophy section of the library -- you encounter not a set of arguments alone, but a person, a mind deploying arguments of diverse kinds, yes, but also other things than arguments: description, rhythm, trope; and always within a language and a context, an already-underway conversation.
To be aware of this is not (or ought not to be) to guard access to competence behind doorkeepers of learning. It is not that "you can't understand Kant without understanding the world he lived in," such that competence in the moves of the first critique would require an armature of previous certifications in Wolff and Leibniz, in Konigsbergian and Prussian politics, in Lutheranism and German typography. It's not even -- though this is truer -- that a grasp, or an appreciation, or an awareness, of any of these adds a dimension to one's feeling for Kant that may or may not be relevant to seeing what he's doing with the synthetic a priori. Talk like that tends to be intimidating, implying that to win the right to an opinion requires fighting ones way through a thicket of prerequisites. But dispel the shadow of the law from all of this, and you find instead the visage of the person. A thinker is a person to know, not a table of positions; they are a style, a stance, and indeed a career. No one knows a person out of context.
Collingwood insists that historical understanding consists in the re-enactment of thought. That re-enactment can't happen unless you are oriented, to some degree, in the same landscape of problems and accepted moves that the thinker inhabited.
The context does not explain, let alone explain away; it does not mean you shrug off Nietzsche's psychologistic readings of whoever, just because you've seen Marx do the trick before. But when you are confronted by the (let us admit) rather overwhelming personalities of "the great philosophers," it can help to see them in their element. Not to "take them down a notch," but to let us hear them better.