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Every theory of knowledge deals with the question of a proof for the truth of knowledge. Leonard Nelson gives reasons that the truth of knowledge is not provable. Nelson's arguments are the subject of this article.
First we will repeat Nelson's definitions for proof, knowledge and truth.
Proof: Derivation of the truth of a sentence from the truth of other sentences
Deduction (example):
B) Every change has its cause.
B´) B is the repetition of an immediate cognition.
B´ is provable. The proof of B´ is the deduction of B.
According to Nelson "immediate cognition" is non-linguistic knowledge. Examples of immediate cognitions are intuitions like "seeing-of-the-red-roof", but also philosophical knowledge, which is a part of our reason (e.g. the principle of causality). Indirect knowledge is linguistic knowledge (e.g. "I see the red roof" or "Every change has its cause").
Nelson differentiates between two kinds of truth:
To distinguish between true and false knowledge we need a criterion: the so called epistemological criterion (or criterion of truth). Nelson shows the inconsistency of such a criterion. The epistemological criterion itself can be knowledge or not. If it is, it has to judge about its own truth. We face a contradiction. If it is not knowledge, we have to explain why it is a criterion of truth. The criterion must therefore be an object of knowledge. This also leads to a circular argument.
Nelson concludes: no epistemological criterion, no theory of knowledge. Nelson's proof is the subject of some articles. To refute the proof, one has to show that the circular argument is avoidable. There is, for example, the attempt by H.A.Schmidt 1. He tries to solve the problem by a staged theory of knowledge. But the problem of the justification of truth arises anew at every stage.
Regardless of the type of the criterion of truth (evidence, consensus, coherence etc.) every theory of knowledge results in a circular argument. Nelson states:
Every theory of knowledge seems to fail at its own "test bed." No theory of knowledge can justify its own truth. The situation reminds one of Baron Münchhausen, who wanted to pull himself out of a swamp by his own bootstraps.
Nelson was looking for his own solution. In his opinion the circular argument results from the -- unjustified -- supposition that knowledge is always a judgment. Every judgement can be reduced to other judgements. This leads to an infinite regress. We face an infinite regress especially if we try to prove the epistemological criterion.
According to Nelson the only way out is to assert the existence of non-linguistic knowledge (immediate cognition). Immediate cognition is the reason for the truth of knowledge. The solution of Nelson is the following: Knowledge is true if it can be reduced to the corresponding immediate cognition. In that way Nelson believes that the infinite regress can be avoided. Could Nelson really avoid the circular argument? We will deal with this question.
Nelson´s epistemological criterion is the following:
KN: .3
x: indirect (linguistic) knowledge; y: immediate cognition (non-linguistic); V(x): x is true; W(x,y): x repeats y; KN: Nelsonian criterion of truth.
But KN is a judgment (indirect knowledge). The Nelsonian criterion of truth leads also to a circular argument. To justify the truth of KN we have to detect an immediate cognition yN that is repeated by KN. Even if we could find such an immediate cognition yN, we have to assume the validity of the following identity:
4.
Thus we have applied the Nelsonian criterion of truth before the justification of its truth. Nelson's solution also fails because of the impossibility to give a criterion of truth that is free of language.
By the way: yN is a very curious kind of knowledge. Because yN (non-linguistic knowledge!) contains information about the truth of sentences.
But there is an additional problem. Because KN is a judgment it faces the problem of the fallibility of indirect knowledge. Fries wrote:
Error belongs to the reflection. A judgment (indirect knowledge) can be false, but an immediate cogniton never can.5
To justify the truth of knowledge, Fries and Nelson refer to the principle of the self-confidence of reason. Nelson gives the following formulation:
It is not the objective validity of knowledge that is in our mind, but the trust in the objective validity.6
But it's not clear to what extent that principle of self-confidence of reason justifies the truth of KN.
Nelson indicates a general problem about attempts to find a firm basis of knowledge. Popper's Friesian trilemma for example is a re-formulation of Nelson's proof of the impossibility of a theory of knowledge. Popper rejects the assumption of an absolute firm basis for scientific knowledge. According to Popper, so called basic sets are the foundation of scientific theories. But there are no distinguished basic sets. We accept basic sets by decision. Every basic set can be checked by other basic sets. There is no natural end.
Kay Herrmann, 2008
| AFSNF | Abhandlungen der Fries'schen Schule. Neue Folge. 1906 - 1937. |
| Nelson, L.: GS | Nelson, L.: Gesammelte Schriften. Hg. von P. Bernays/ W. Eichler/ A. Gysin/ G. Heckmann/ G. Henry-Hermann/ F. v. Hippel/ S. Körner/ W. Kroebel/ G. Weisser. 9 Bde., Hamburg 1970 - 1977. |
| Fries, J. F.: WW | Fries, J. F.: Sämtliche Schriften. Nach den Ausgaben letzter Hand zusammengestellt, eingeleitet und mit einem Fries-Lexikon versehen von G. König/ L. Geldsetzer. (Bisher) 26 Bde., Aalen 1967 - 1997. |
Fries, J. F.: System der Logik. 3. Aufl., Heidelberg 1837 (WW 7, p. 153 - 632).
Nelson, L.: „Die Unmöglichkeit der Erkenntnistheorie“. In: GS 2, pp.459 - 483. "The Impossibility of the 'Theory of Knwoeldge'," Socratic Method and Critical Philosophy, translated by Thomas K. Brown III, Yale, 1949, Dover, 1965.
Nelson, L.: Fortschritte und Rückschritte der Philosophie. Von Hume und Kant bis Hegel und Fries. Aus dem Nachlaß herausgegeben von Julius Kraft. In: GS 7. Progress and Regress in Philosophy, Vol. I & II, translated by Humphery Palmer, Basil Blackwell, Oxford, 1970, 1971.
Schmidt, A.: Der Beweisansatz von L. Nelson für die „Unmöglichkeit der Erkenntnistheorie“ als Beispiel eines retroflexiven Schlusses. In: Argumentationen. Festschrift für Josef König. by H. Delius/ G. Patzig. Göttingen 1964, p. 216 - 248.
Jakob Friedrich Fries (1773-1843)
1. Schmidt, A.: Der Beweisansatz von L. Nelson für die „Unmöglichkeit der Erkenntnistheorie“ als Beispiel eines retroflexiven Schlusses.
2. Nelson: „Die Unmöglichkeit der Erkenntnistheorie“, p.465.
3. KN: An indirect knowledge x is true if and only if there exists an immediate cognition y so that KN repeats y.
4. KN is true if and only if there exists an immediate cognition y so that KN repeats y.
5. Fries: System der Logik, S. 341 (WW 7, S. 509).
6. Nelson: Fortschritte und Rückschritte der Philosophie, p.630.