[7.5.] Peirce’s Objection to the Information-Relative Account of Substantial Possibility.

 

Peirce’s objection to the IR account of substantial possibility seems to have been as follows...

 

On the IR account...

 

·         substantial logical possibility is a matter of ignorance, viz.

 

It is substantially logically possible that p if and only if a hypothetical person who knows all past facts and general laws would not know that it is not true that p.

 

It is substantially logically possible that p because it is not known that it is not true that p.

 

·         substantial logical impossibility is a matter of knowledge, viz.

 

It is substantially logically impossible that p if and only if a hypothetical person who knows all past facts and general laws would know that it is not true that p.

 

It is substantially logically impossible that p because it is known that it is not true that p.

 

Peirce rejected the view that it is substantially logically impossible that p because it is known that it is not true that p. His objection seems to be that this gets things backwards.

 

Says Peirce, a person knows that it is untrue that p because he sees that it is substantially logically impossible that p. Says Peirce: “We know in advance of experience that certain things are not true, because we see they are impossible.”

 

He goes on to give the following example:

 

Thus, if a chemist tests the contents of a hundred bottles for fluorine, and finds it present in the majority, and if another chemist tests them for oxygen and finds it in the majority, and if each of them reports his result to me, it will be useless for them to come to me together and say that they know infallibly that fluorine and oxygen cannot be present in the same bottle; for I see that such infallibility is impossible. I know it is not true, because I satisfy myself that there is no room for it even in that ideal world of which the real world is but a fragment. I need no sensible experimentation, because ideal experimentation establishes a much broader answer to the question than sensible experimentation could give. It has come about through the agencies of development that man is endowed with intelligence of such a nature that he can by ideal experiments ascertain that in a certain universe of logical possibility certain combinations occur while others do not occur. (CP 3.527; modality handout, selection 3)

 

The example seems to be as follows: Suppose that someone knows the following two claims to be true:

 

A. Fluorine is present in the majority of a set of bottles.

B. Oxygen is present in the majority of that same set of bottles.

 

Given this, no further experience is needed for her to “see” that the following claim is not true:

 

C. Fluorine and oxygen cannot be present in the same bottle.

 

It is not that (C) is impossible because someone who knows (A) and (B) would know, or judge, that (C) is not true.

 

Rather, someone who knows (A) and (B) will judge that (C) is not true because she will see that, given (A) and (B), it is impossible that (C).

 

In general:

·         whether a claim is substantially logically impossible does not depend on what someone in a hypothetical or “feigned” state of information would know to be false.

·         rather, we know (some) things to be false because we “see” them to be substantially logically impossible: “It is not that certain things are possible because they are not known not to be true, but that they are not known not to be true because they are, more or less clearly, seen to be possible.” (CP 6.367, modality handout, selection 5)

 

 

[7.6.] The “Great Step.”

 

Roughly eight years after he rejected the IR account of substantial logical possibility, Peirce looked back on that decision and wrote:

 

... In the Monist of Jan. 1897 [“The Logic of Relatives” (1897), selection 3 in the modality handout] quite assertorically, ... and this same journal during 1892 more tentatively,[1] the author of the present article repudiated the nominalistic view of possibility, and explicitly returns to the Aristotelian doctrine of a real possibility.  This was the great step that was needed to render pragmaticism an intelligible doctrine. The paper of Jan. 1878 [“How to Make Our Ideas Clear”] wavers palpably at this point, sensible of the advantages of a real possibility, yet wishing to save pragmaticism in case that doctrine should prove untenable.  Its author had long before argued for real generals, from which it follows pretty obviously that there are real necessities; and that granted, one expects real possibility to stand by its side.

It must be said, however, that [“The Logic of Relatives”] is confined to ideal possibility and that it by no means affords a completely satisfactory account even of that. Nor shall I now pretend to lay bare the whole theory of modality. It is far too great a question to be treated incidentally to any other. (modality handout, selection 6)[2]

 

In another manuscript from the same period, Peirce wrote:

 

In [“Logic of Relatives,” (1897)] the objectivity of possibility was asserted; and the hypothesis defended in [“The Architecture of Theories” (1891) and “The Doctrine of Necessity Examined” (1892)][3] supposes possibility to be real.  It was, indeed, implied in the scholastic realism maintained in the [review of Fraser’s Works of George Berkeley (1871)]. But the paper of January 1878 [“How to Make Our Ideas Clear”] evidently endeavors to avoid asking the reader to admit a real possibility.  The theory of modality is far too great a question to be treated incidentally to any other.  But the distinct recognition of real possibility is certainly indispensable to pragmaticism. (modality handout, selection 8)[4]

 

These passages indicate all of the following:

 

·         Peirce was not satisfied with the account of “ideal” (substantial logical) possibility he gave in 1897.

 

·         There is a sense in which Peirce was a realist about modality before 1897: realism about modality is implied both by tychism and pragmatism (“pragmaticism”). [This is why the 1897 modal shift is not a complete about-face. It is, rather, the move from weak realism about modality to strong realism about modality.]

 

·         There is a sense in which the IR account of possibility is nominalistic—a view of modality that a nominalist, someone who denies the reality of generals, might be tempted to adopt. This is supported by what Peirce wrote about the IR definition in 1902:

 

The nominalistic definition (nominalistic in its real character, though generally admitted by realists, as Scotus, i. dist. 7, qu. unica) that that is possible which is not known not to be true in a real or assumed state of information is, like many nominalistic definitions, extremely helpful up to a certain point, while in the end proving itself quite superficial. (CP 6.367, 1902; modality handout, selection 5)

 

From at least the mid 1880s until 1897, Peirce was himself one of those realists who “admitted” a definition of possibility which, at the time, he took to be compatible with his realism, but which he came to believe was ultimately nominalistic.

 

·         The modal shift, from weak modal realism to strong modal realism, was decisive, so much so that it “rendered pragmaticism an intelligible theory.”

 

Selections 7 and 8 in your reading for today illustrates how Peirce’s new, strong modal realism has consequences for Peirce’s pragmatism and his scholastic realism. We will be examining these consequences over the next several classes.

 

 

Stopping point for Friday October 19. For next time, read EP 2:179-83 (down to the paragraph beginning “No.2. You may...”)