In 1919 Wittgenstein wrote to von Ficker:
The book’s point is an ethical one. I once meant to include in the preface a sentence which is not in fact there now but which I will write out for you here because it will perhaps be a key to the work for you. What I meant to write, then, was this: My work consists of two parts: the one presented here plus all that I have not written. And it is precisely this second part that is the important one. My book draws limits to the sphere of the ethical from the inside as it were, and I am convinced that this is the rigorous way of drawing those limits. In short, I believe that where many others today are just gassing, I have managed in my book to put everything firmly into place by being silent about it. And for that reason, unless I am very much mistaken, the book will say a great deal that you yourself want to say. Only perhaps you won’t see that it is said in the book. For now, I would recommend you to read the preface and the conclusion, because they contain the most direct expression of the point of the book.
I have quoted from this exchange in The New York Review of Books between Allan Janik and D. F. Pears. Here is (part of) the German:
Es wird nämlich das Ethische durch mein Buch gleichsam von Innen her begrenzt; und ich bin überzeugt, daß es, streng, NUR so zu begrenzen ist. Kurz ich glaube: Alles das, was viele heute schwefeln, habe ich in meinem Buch festgelegt, indem ich darüber schweige.
I can't improve on the translation, but 'rigorous' to my mind can suggest something like the thorough application of a method, something technical, and I don't think streng has this implication. I might be wrong. Google translate suggests 'strictly,' which has exactly that connotation. But the similarity between the German 'streng' and the English 'strong' makes me think that it means something like 'properly' or 'in a way that is not weak or lame' in this context.
The idea of delimiting or defining the ethical from within is a curious one. It suggests to me something like a rejection of any foundationalism in ethics, of any attempt to answer a question like 'Why be good?' If we are (always already, if you like) within ethics, after all, then it seems we must in some sense take it as given. But this isn't what you find in the Tractatus at all. Questions about value are not addressed until the end of the book, and then we are told (in 6.41) that value can only lie outside the world. Perhaps the Tractatus itself is somehow meant to be written from outside the world, which it seemingly would have to be if it were written from within ethics (and if ethics lies outside the world), but it seems more likely that when Wittgenstein says his "book draws limits to the sphere of the ethical from the inside" he means from the inside of the book, not from the inside of ethics. The strategy of the book would then be something like this: it would be written from a supposedly extra-ethical vantage point, somewhere almost Nietzschean in its coldness and hardness (I'm thinking of Nietzsche as portrayed here), somewhere very much in the logical-positivist or scientistic sphere (speaking aesthetically or in terms of flavor, that is); it would then draw the limit of the sphere of the ethical by showing that there is no such limit, that there is nothing beyond ethics, nothing that value cannot reach; and it would have to do this by showing that the book's own vantage point is merely imaginary, that the book as presented does not, cannot, exist. It must explode itself, slowly, as one reads, turning itself inside out under the pressure of its self-appointed impossible task (i.e. existing outside the sphere of the ethical). Then we might see that the place we had imagined to exist beyond the ethical does not exist, that we had only imagined that we could see beyond the horizon of value.
A somewhat similar idea, used in a different way, is found in the Lecture on Ethics:
And now I must say that if I contemplate what Ethics really would have to be if there were such a science, this result seems to me quite obvious. It seems to me obvious that nothing we could ever think or say should be the thing. That we cannot write a scientific book, the subject matter of which could be intrinsically sublime and above all other subject matters. I can only describe my feeling by the metaphor, that, if a man could write a book on Ethics which really was a book on Ethics, this book would, with an explosion, destroy all the other books in the world. Our words used as we use them in science, are vessels capable only of containing and conveying meaning and sense, natural meaning and sense. Ethics, if it is anything, is supernatural and our words will only express facts; as a teacup will only hold a teacup full of water and if I were to pour out a gallon over it.I'm waiting for someone on this thread to say that work on the history of philosophy (e.g work on what Kant really thought about x or Plato meant by y) is worthless and that only practical or scientific work has any value. With that in mind, who cares what Wittgenstein meant? Well, I do, I suppose. But I think what concerned him continues to concern people, albeit perhaps in different ways. One way to attack ethics (or religion) is to treat it scientifically. If we trace the origins of morality (or religion) to something in our evolutionary history, say, then we are likely to seem not only to have explained something but to have debunked it. Nietzsche tried to do something like this quite deliberately, and empirically-minded ethicists (sometimes) do it unwittingly. For an example of how the attempted debunking of religion in this way might go see here. The link is to Brian Leiter on a review of Daniel Dennett's tellingly titled Breaking the Spell, in which Leiter writes that:
It is true that you cannot show a belief to be false by explaining its origin, but it is clear you can show that holding the belief is not warranted by explaining its origin. (This is an important topic I have dealt with elsewhere.) If you believe buying stock in High Tech Miracle, Inc. is a good investment based on recommendation of your broker, and then you discover that your broker recommended it because he is an investor in the company and a beneficiary of its rising stock fortunes, you no longer have a reason to believe it's a good investment--though it might turn out to be one, of course, but you no longer are warranted in believing that. Hume, Nietzsche, Marx, Dennett and many others exploit this form of argumentation, without making any mistakes, let alone abandoning "reason," as Mr. Wieseltier--whose arrogance may even outstrip his ignorance--remarkably claims.For the case of ethics, see here. The link is to Helen De Cruz on "evolutionary debunking arguments" in which she paraphrases Sharon Street as holding:
that, even if there were universal agreement about moral evaluative attitudes, this would not constitute any evidence for moral objectivism, because an evolutionary account can plausibly [explain] why we hold those beliefs without invoking any objective moral norms. Indeed, it would be highly unlikely, an incredible coincidence, if this were the case
So if we all agree that murder is wrong, and if evolutionary accounts can explain why we believe this, then it would be highly unlikely that we believe murder is wrong because it really is wrong. At least, I think that's what the idea is. And the effect, I think, is to undermine our belief that murder is wrong, to push us toward a kind of defensiveness about our moral commitments. So "murder is wrong" becomes "murder is wrong (in my opinion, of course, but that's just an accident of history--I'm not so naive as to think I have any insight into the Truth)."
The key word (in "explaining why we believe this or that") is 'why.' The evolutionary account is historical or causal. It is not rational or justificatory. It would not be an incredible coincidence if I hold that murder is wrong because (in the justificatory sense) it really is and I also hold that murder is wrong (in the causal, historical sense) because I belong to a species that has this belief for evolutionary reasons (i.e. because of evolutionary processes). Nor would it be an incredible coincidence if the (let us suppose) useful belief that murder is wrong is actually true, even (or especially) if 'true' does not simply mean 'useful'. I say especially here because the sense in which a moral belief is true might be part of a completely different ballgame from that in which a judgment about the world is true or false. It is not an incredible coincidence if I check my watch at the same time that I check my bags. It is a sort of pun or accident (non-necessary, not utterly random, feature) of language. Similarly, it is a sort of accident if useful beliefs are also worthy of affirmation. (What might not be a mere coincidence is that such beliefs are deemed worthy of affirmation. But that's a separate issue.)
[I remember thinking that I had realized something was wrong with this, but I can't remember what it was.]
What Wittgenstein might have meant is that in the Tractatus he tackles ethics from the outside. From within an 'objective' or 'scientific' position he tries to show that such a position is untenable, that the ladder collapses. And thus that what the Tractatus rules out as nonsense is in fact not some separable sphere but part of the only sphere there is, the only game in town: sense or the intelligible world (in a non-metaphysical sense). Then, continuing with my speculation (or half-remembered ideas taken from others, if that's what these are), the Investigations would more truly be a work of ethics (and everything else) from within.
Look at this wriggling fly and see what happens when you tell yourself that its pain is not real (I'm thinking of PI 284, although this isn't exactly what he says there--it's more that a fly can be believed to be in pain). Look at those children and tell yourself that they are automata (PI 420). You cannot prove the contrary, but you cannot believe these things. You do not believe them. Or, at any rate, we do not believe them (which is a kind of definition of 'we'). This is philosophy done from within ethics, from within the world of ordinary judgments, from within our (partly) subjective experience of the world, not in some pretend-objective way. A certain ideal of objectivity is illusory, because it would be outside ethics, outside value judgment, outside all normativity and subjectivity, and there is no such sphere.