Online research in philosophy

The first part of the article deals with the theories of probability and induction put forward by Hans Reichenbach and Rudolf Carnap. It will be argued that, despite fundamental differences, Carnap's and Reichenbach's views on probability are closely linked with the problem of meaning generated by logical empiricism, and are characterized by the logico-semantical approach typical of this philosophical current. Moreover, their notions of probability are both meant to combine a logical and an empirical element. Of these, Carnap over the years put more and more emphasis on the logical aspect, while for Reichenbach the empirical aspect has always been predominant. Seen in this light, Carnap's and Reichenbach's theories of probability can be taken to represent the Viennese and Berlinese mainstreams of the common logical empiricist approach. The second part of the article contrasts the position of these authors with that of the Bruno de Finetti, who is the main representative of the subjective interpretation of probability. Though the latter is sometimes associated with the position taken by Carnap in his late writings, it will be argued that the two are in many ways irreconcilable.

Nelson, L. The impossibility of the "Theory of knowledge."--Moore, G. E. Four forms of skepticism.--Lehrer, K. Skepticism & conceptual change.--Quine, W. V. Epistemology naturalized.--Rozeboom, W. W. Why I know so much more than you do.--Price, H. H. Belief and evidence.--Lewis, C. I. The bases of empirical knowledge.--Malcolm, N. The verification argument.--Firth, R. The anatomy of certainty.--Chisholm, R. M. On the nature of empirical evidence.--Meinong, A. Toward an epistemological assessment of memory.--Brandt, R. The epistemological status of memory beliefs.--Malcolm, N. A definition of factual memory.--Martin, C. B. and Deutscher, M. Remembering.--Ayer, A. J. Basic propositions.--Reichenbach, H. Are phenomenal reports absolutely certain?--Goodman, N. Sense and certainty.--Lewis, C. I. The given element in empirical knowledge.--Alston, W. Varieties of privileged access.--Schlick, M. The foundation of knowledge.--Russell, B. Epistemological premisses, basic propositions, and factual premisses.--Firth, R. Coherence, certainty, and epistemic priority.--Sellars, W. Empiricism and the philosophy of mind.--Quinton, A. The foundations of knowledge.

This paper is a sympathetic critique of the argument that Reichenbach develops in Chap. 2 of Experience and Prediction for the thesis that sense experience justifies belief in the existence of an external world. After discussing his attack on the positivist theory of meaning, I describe the probability ideas that Reichenbach presents. I argue that Reichenbach begins with an argument grounded in the Law of Likelihood but that he then endorses a different argument that involves prior probabilities. I try to show how this second step in Reichenbach’s approach can be strengthened by using ideas that have been developed recently for understanding causation in terms of the idea of intervention.

Some philosopheis (e.g. Ayer, Reichenbach, Lewis) use a version of the argument from illusion to prove that empirical statements are never certain. But this argument, unwittingly, also calls into doubt the certainty of calculations in logic and mathematics. The argument seems to call into question the application of any rule on the grounds that one might at some future time find out that one had misapplied it. But the argument from illusion is only the illusion of an argument.

Hans Reichenbach is well known for his limiting frequency view of probability, with his most thorough account given in The Theory of Probability in 1935/1949. Perhaps less known are Reichenbach’s early views on probability and its epistemology. In his doctoral thesis from 1915, Reichenbach espouses a Kantian view of probability, where the convergence limit of an empirical frequency distribution is guaranteed to exist thanks to the synthetic a priori principle of lawful distribution. Reichenbach claims to have given a purely objective account of probability, while integrating the concept into a more general philosophical and epistemological framework. A brief synopsis of Reichenbach’s thesis and a critical analysis of the problematic steps of his argument will show that the roots of many of his most influential insights on probability and causality can be found in this early work.

Reichenbach’s use of ‘posits’ to defend his frequentistic theory of probability has been criticized on the grounds that it makes unfalsifiable predictions. The justice of this criticism has blinded many to Reichenbach’s second use of a posit, one that can fruitfully be applied to current debates within epistemology. We show first that Reichenbach’s alternative type of posit creates a difficulty for epistemic foundationalists, and then that its use is equivalent to a particular kind of Jeffrey conditionalization. We conclude that, under particular circumstances, Reichenbach’s approach and that of the Bayesians amount to the same thing, thereby presenting us with a new instance in which chance and credence coincide.

From 1929 onwards, C.I. Lewis defended the foundationalist claim that judgements of the form ‘x is probable’ only make sense if one assumes there to be a ground y that is certain (where x and y may be beliefs, propositions, or events). Without this assumption, Lewis argues, the probability of x could not be anything other than zero. Hans Reichenbach repeatedly contested Lewis’s idea, calling it “a remnant of rationalism”. The last move in this debate was a challenge by Lewis, defying Reichenbach to produce a regress of probability values that yields a number other than zero. Reichenbach never took up the challenge, but we will meet it on his behalf, as it were. By presenting a series converging to a limit, we demonstrate that x can have a definite and computable probability, even if its justification consists of an infinite number of steps. Next we show the invalidity of a recent riposte of foundationalists that this limit of the series can be the ground of justification. Finally we discuss the question where justification can come from if not from a ground.