Wittgenstein on “I may be dreaming”
In On Certainty, Wittgenstein remarks that a certain argument is senseless, namely the argument that I may be dreaming:
383. The argument “I may be dreaming” is senseless for this reason: if I am dreaming, this remark is being dreamed as well—and indeed it is also being dreamed that these words have any meaning.
It must be kept in mind that On Certainty is first draft material, which Wittgenstein did not live to edit. (If the remark is an attempt to dispel dream scepticism, I don’t think it works.) In any case, here is an effort to reconstruct Wittgenstein’s thinking above.
(1) The conclusion of an argument that I may be X must be formulated in words that have meaning, including in a context in which the words are used by me while the possibility identified is realized; otherwise the argument itself is senseless.
(2) The argument that I may be dreaming is an argument that I may be X, where the possibility identified is that I am dreaming and the words used to formulate the conclusion are “I may be dreaming”.
(3) Words used by me do not have any meaning if they are being dreamt of by me as having meaning.
(4) All words used by me while I am dreaming are being dreamt of by me as having meaning.
From (1) and (2):
(5) If the words “I may be dreaming” do not have any meaning, in a context in which the words are used by me while I am dreaming, the argument that I may be dreaming is senseless.
From (3) and (4):
(6) The words “I may be dreaming” do not have any meaning, in a context in which the words are used by me while I am dreaming.
From (5) and (6):
(7) The argument that I may be dreaming is senseless.
Regarding the first premise, it is concerned with arguments that both identify a possibility for me and also represent the possibility as something that I cannot rule out: for all I know, the possibility is actualized at the time when I make the argument. Arguments that only identify the possibility are not of concern. Regarding the claim of senselessness in this premise, I understand Wittgenstein as implying that my (seeming) assertion of the conclusion must be meaningful both if the possibility is realized and if it is not, or else my (seeming) assertion in either circumstance is meaningless. Regarding the fourth premise, perhaps Wittgenstein wishes to deny that words are in fact used by me when I am dreaming – I merely dream that they are used by me. But I think the current formulation of his thinking is adequate for assessing it. Any objections should transfer over to other formulations.
Wittgenstein, L. (translated by D. Paul and G.E.M. Anscombe, edited by G.E.M. Anscombe and G.H. von Wright) 1979. On Certainty. Oxford: Basil Blackwell.