Full Idea
We are considering that there is something in ravens, a gene perhaps, that makes them black, and this cause is part of the essence of ravens. Birds lacking this cause could not interbreed with ravens.
Gist of Idea
If something in ravens makes them black, it may be essential (definitive of ravens)
Source
Peter Lipton (Inference to the Best Explanation (2nd) [2004], 05 'Unsuitable')
Book Reference
Lipton,Peter: 'Inference to the Best Explanation (2nd ed)' [Routledge 2004], p.97
A Reaction
At last, the essentialist approach to induction! Of course, it is tricky to decide a priori whether there could be albino ravens. It only takes one white (interbreeding) raven to ruin a nice essentialist story. Individuals matter.
Related Idea
Idea 15287 The possibility that all ravens are black is a law depends on a mechanism producing the blackness [Harré/Madden]