Competencia investigativa y de satisfacción

The first step in Neurath's argument is to argue that a protocol sentence cannot merely be along the lines of "here now blue". Rather, he says, all protocol sentences must include a proper name. Protocol sentences always express the experiences of somebody,22_{and sentences in the language of science couldn’t contain indexicals or}

demonstratives like “I” or “here” without losing their intersubjectivity. That means that a complete protocol sentence will read along the lines of "Otto's protocol at 3.15: [at 3.14 Otto said to himself: (at 3.13 there was a table in the room perceived by Otto)]" (Neurath, 1932, [1959, p.202]). The innermost set of brackets in the protocol statement contains a perception which is attributed to a specific person, and importantly the perception is intersubjective – it is perception of a physical fact rather than a phenomenal description of the perception (in other iterations of the proposal, Neurath suggested an additional set of brackets so that the innermost was a straightforward factual statement like “there was a table in the room” and the next layer out was something like “at 3.13 Otto perceived:” (Uebel, 2007, p.379)) . We could construct protocol sentences without the set of brackets containing "Otto said to himself", (e.g. "Otto's protocol at 3.15: [at 3.14 there was a table in the room perceived by Otto]") but it is useful to Neurath's argument to note that we can use sentences of the same form as protocol statements to describe people's experiences when they are hallucinating or lying (e.g. "Otto's protocol at 3.15: [at 3.14 Otto wrote: (at 3.13 there was a square circle in the room perceived by Otto)]").

22 _{This is in stark contrast to Carnap's position in the Aufbau, where he had an entire section}

titled "The Given Does Not Have a Subject" (§65) about why experiences did not have to be linked to an individual. We will return to Carnap's position on this matter in section 4.4.1, as there is some scope for interpretation on this point.

- 105 -

Having introduced this formal structure Neurath points out that protocol sentences are statements of fact. And, like other statements of fact, they are subject to disconfirmation. Neurath asks us to imagine a scholar who can write with both his right and left hands at the same time. Suppose that the scholar writes a protocol sentence with each hand at the same time, and suppose further that the two sentences directly contradict one another. Clearly the two sentences cannot both be true. Therefore, protocol sentences cannot be sentences which require no confirmation.23

Neurath reiterates a point made by Carnap that science consists in forming a non-contradictory system of protocol and non-protocol sentences. However, since protocol sentences are just as subject to revision as non-protocol sentences, if we are faced with a protocol statement which conflicts with our system as it stands then we are not forced to reject the system - we can reject the protocol sentence. "A defining condition of a sentence is that it be subject to verification, that is to say, that it may be discarded," (Neurath, 1932, [1959, p.204]). Since no sentence is held to be true on its own, on Neurath's view it appears that the truth of a statement consists in nothing more than the mutual agreement of that statement with all of the other statements in the system. This is what is known as a "coherence theory of truth", and it is as opposed to a "correspondence theory of truth" under which the truth of a statement consists in it accurately reporting facts. The coherence theory of truth

23 _{At first sight this argument seems so obvious that it must have missed the point}

somewhere. Even without the preceding discussion about the form of protocol sentences, it seems clear to us that for any sentence about immediate experience there is a similar sentence about a different experience mutually exclusive with the first. Clearly, we cannot work out just from looking at one such sentence whether or not it is true. Neurath's argument appears to have gone unnoticed for so long because the Vienna Circle did not think of propositions in the same way as we do today. Instead of there being infinitely many propositions, any of which a given utterance may or may not assert, they would have said that for a proposition to exist was for it to be asserted. Hence the contradiction only arises when someone actually asserts two conflicting propositions at the same

time, as with Neurath's ambidextrous scholar. In fact, the outermost set of brackets, “Otto’s protocol at 3.15…” is considered satisfied only if what follows is in fact entered into the scientific record (Uebel, 2007, pp.383-384). It is an important part of Neurath’s philosophy that science is a social

endeavour and that coherence is to be strived for within the sets of statements that people are in fact making, not merely within any arbitrary group of possible statements.

- 106 -

is, as we shall see, at the root of Schlick's complaints against Neurath, although it may not be attributed to him fairly (which we will return to from section 4.4.2 onwards).

Neurath argues that we should abandon any notion of a difference between our own protocol sentences and those of anyone else. It might be thought that we could be more certain about our own experiences than those of anyone else, but Neurath points out that memory is fallible, and for all intents and purposes a protocol sentence we wrote yesterday might as well have been written by someone else. We can imagine, for example, a person losing his memory and rediscovering his life by reading through a list of previously written protocol sentences, but we can just as well imagine him learning the history of someone else's life by doing so. Hence, we need an intersubjective protocol language for thinking about our own experiences just as much as we would need one for talking about someone else's. (This argument pre-empts the private language argument later attributed to Wittgenstein by some twenty years.)

Neurath's arguments showed that protocol sentences couldn't be formed in a private protocol language before being translated into the physical language, as Carnap had envisaged them. They would have to be part of the physical language to begin with. But, as part of the physical language, they lost both their connection to phenomenal sense data and their privileged epistemic status. In the next section we will look at the positive proposal which Neurath and Carnap built to address these problems, and in particular we will look more closely at the coherence theory of truth which they adopted.