I listened to the lecture by Hoppe (http://media.mises.org/mp3/MU2008/4_Hoppe.mp3) and I disagree with some of his defences of Austrian reasoning, and some of his attacks on logical positivism.
For instance, he says that if he deduces an economic statement from certain axioms, such as law of marginal utility, then he knows that this statement is true. Hoppe claims that he knows with absolute certainty that the conclusion of any deductive argument is true, and so there is no need for empirical testing. To use another of his examples, he knows that having a minimum wage of $1000 per hour would lead to a rise in unemployment, and there is no need to test this. Hoppe’s mistake is not realising that we must be certain that the axioms of a deductively valid argument are true if we are to be certain that the conclusion is true. However, we cannot know that our axioms are true with certainty, because all axioms are in essence assumptions. An a priori statement is one which we take to be true for the purposes of argument; the mistake here is assuming that this means that an a priori statement is in fact true. Hoppe claims that some a priori are self-evident truths, which are ‘unfalsifiable’.
(By the way, he uses the term ‘unfalsifiable’ incorrectly; he takes it to mean that a statement is unfalsifiable if it cannot be shown to be untrue because it is true, whereas the correct usage would be that a statement is unfalsifiable if it cannot be shown to be untrue in principle; that is, because there is no observation or experiment that could even attempt to show that it is false.)
However, there is no justification for assuming self-evident truths, or that a priori statements are true. There is by definition no deductive basis for an a priori statement, so how can we be certain that it is true? The only possible justification we can have for assuming the truth of a priori statements, if we have any at all, is inductive. That is not to say that a priori statements are inherently unreasonable, merely that we cannot be certain of their truth, in the same way that all conclusions of inductive reasoning are inherently uncertain, even if reasonable.
An example is Euclidean geometry, which is in fact mentioned in one of the articles defending Austrian reasoning (http://mises.org/daily/1304). With the axioms of Euclidean geometry, one can deduce all sorts of results, which are all true as long as the axioms underpinning Euclidean geometry are true. But we do not know that these axioms are true. People believed they must be true for a long time, because they were taken to be self-evidently true. However, if you take different axioms you end up with different spaces and different results. Indeed, modern science believes that the space we inhabit is in fact non-Euclidean, so the laws that people like Hoppe might have been absolutely certain about, like that the shortest distance between two points is a straight line, are not necessarily true.
I also disagree with his main attack on logical positivism, which is that it relies on an assumption of constancy. He then argues that it is impossible to obtain constancy, and so logical positivism is inherently flawed. His argument is as follows:
Suppose I have a hypothesis, if A then B. I then observe A, followed by B. This observation ‘confirms’ the hypothesis, but only in the strict sense of confirmation which Hoppe defines. I then, at a later date, again observe A followed by B. I would then argue that this second observation confirms the first observation. Hoppe says that this is only the case if there is a constancy over time between the two observations; if the nature of A or B has changed between the two observations, then the second observation can neither confirm nor falsify the first. The argument then continues that any observation or experiment must be made by an observer, who must learn from his observations, otherwise what is the point of observing? Because the observer learns after each observation, there is therefore no constancy between observations, and so logical positivism is flawed.
However, there are a number of problems with this argument. To begin with, he uses confirm in the wrong sense, indeed contradicting his own definition of confirm, which is reasonable from Popper’s perspective. That is, he talks about confirming or falsifying observations, but that is nonsensical. One can only talk about confirming or falsifying hypotheses. When one makes an observation, then another observation, these observations neither confirm nor falsify one another; they are merely separate observations. One observation may confirm a hypothesis, whilst the other falsifies it, or vice versa for another hypothesis, but it doesn’t make any sense to talk about observations confirming or falsifying one another.
Furthermore, Hoppe makes the logical mistake of assuming that if A changes, then A is still A, when this is by definition false. If A changes it is not A, but rather something else, which we can label A’. Returning to the original hypothesis of if A then B, and we observe A’ followed by B’, then this is a different phenomenon from A followed by B, and so neither directly confirms nor falsifies the hypothesis. Thus no assumptions about constancy are necessary at all. Furthermore, if the rule governing relation between A and B changes, that is the hypothesis is ‘true’ at one point in time but false at another, then the hypothesis, is, strictly speaking, false, because it requires A to always be followed by B.
As an aside, I don’t think Hoppe is strictly speaking about logical positivism, but rather mixing elements of Popper’s philosophy with that of the logical positivists. He takes Popper’s view that hypotheses cannot be verified; one can only fail to falsify a hypothesis, which is the definition he takes of ‘confirm’, whereas the positivists thought that meaningful statements could be determined to be true or false. Also, I suspect Hoppe is confused by the concept of causality. Causality has no place in logic; to say A implies B in no way implies a causal relation between A and B.
And I would strongly disagree to say philosophy is not science.