Hempel’s Paradox of the Ravens
By Murali Ramachandran (Witwatersrand, Philosophy)
Date: Thursday, 5th March, 2020
Time: 1540-1710
Place: H-232
Abstract: Hempel’s paradox of the ravens arises from two very compelling principles, SUPPORT and EQUIVALENCE:
SUPPORT
Observations of FGs support (confirm, count as positive evidence for) the hypothesis ‘All Fs are G’, so long as no non-G Fs have been observed.
(E.g. observations of tigers with stripes supports the hypothesis [All tigers have stripes], so long as tigers without stripes have not been observed.)
EQUIVALENCE
Evidence that supports a hypothesis equally supports any logically equivalent hypothesis.
(E.g. any evidence which supports [There are Latvian vegetarians] equally supports [There are vegetarian Latvians])
Now consider the following statements:
[Rave] All ravens are black.
[NoB] All non-black things are non-ravens.
These are logically equivalent: one cannot be true without the other being true as well. By SUPPORT, observation of a red pencil, say, being an observation of a non-black nonraven, supports hypothesis [NoB], and thus, by EQUIVALENCE, also supports hypothesis [Rave] that all ravens are black.
It is at least prima facie paradoxical that a red pencil should count as positive evidence for a hypothesis about ravens!
This is Hempel’s paradox of the ravens. My goal in this talk is to explain why I think causal realists—that is, just about all of us(!)—escape the paradox.
(Those already familiar with the paradox can get a foretaste of my position by looking at my paper here)
About the speaker: Murali Ramachandran’s research is focused on metaphysics, philosophy of language and philosophical logic. He is currently Associate Professor in philosophy at Witwatersrand University. Previously he taught at Trinity College Dublin, Manchester University and Sussex University. He has published in journals such as Mind, Philosophical Quarterly, Australasian Journal of Philosophy, Philosophical Studies and Analysis.
