As Esther-Mirjam Sent aptly suggests, the question is what constitutes "proof" in empirical social (or for that matter natural) science. Rather than talk of "proof" we could perhaps talk of soundness of argument. As so much of the rhetoric of economics literature has made clear, this is a complex subject. Let me offer one take on it. One thing that many natural scientists do to try to establish the reliability of their empirical work is to make sure that it can be replicated. Clearly specifying one's data, the kind of equipment one is using, the computer software used to analyze it etc. are all ways of letting other researchers retrace the scientist's steps to see whether the same result would occur. One could argue that the process of scholarly reference and citation in the history of economics is analogous to the replication process in the natural and social sciences. What careful and accurate scholarship does is to say to one's reader "Go back and retrace my sources and look at what they said and did and try to understand why I would draw my conclusions from this." Of course such a process can never be "proof" nor should we expect all reasonable readers of sources to come to the same conclusions. Nonetheless, careful scholarship, in this sense, is necessary (although, again, not sufficient) to generate quality arguments and any degree of scholarly consensus. To hold ourselves to standards of "proof" beyond this is a sure path to permanent disappointment. Vain hopes for extra-human standards of proof need to be replaced with realistic hopes for human standards of discourse, scholarship, and scholarly consensus. Steve Horwitz St. Lawrence University