The statement "all ravens are black" is false.
Just like the philosophical chestnut "all swans are white" was refuted when those pesky explorers discovered Australia (and along with it a refutation of almost every biological category) this claim has long been proven false through the judicious use of eyesight.
Yet again reality has thrown the epistemologist another curve ball with the albino raven.
An albino type raven crops up about one in every 10,000 eggs. Most of the time those birds will have only partial colour loss and so is technically a "leucistic" or "partial albino" raven. However in very very rare cases an entirely white raven will emerge. The last recorded incidence of a truly albino raven sadly died in 1997 in Port Clements Canada.1
The existence of white ravens might shock some of the more readily shockable philosophers, but to classicists, folklorists and corvidologists it will come as no surprise.
After all, mythologically speaking, ravens were originally white.
According to Greek legend, Apollo fell in love with the mortal Coronis and appointed a raven to look over her while she was pregnant with his child. When Coronis fell in love with Ischys and married him, the raven told the God about the wedding. After Apollo had destroyed the newlyweds in a fit of rage he turned all ravens black for being the bearers of bad news.
(This appears to be something of a habit for Apollo as in another story he turned all crows black for other message related reasons.)
Odin is famous for his two ravens Huginn and Muninn but he also seems to have a connection with white raven:
There are nights when the moon shines so brightly
and everything is ever so quiet.
Then Odin rides through the forest.
These are the raven nights.
When all the ravens are white and can speak,
and everyone can understand them 2
This could just be a way of saying that raven nights are very dark, but the more literal interpretation would be that during special nights when the raven are most capable they become white.
Some Native American tribes use the white raven to explain the position of heavenly bodies and the creation of fire:
The raven saw the sun, moon, stars and a burning stick being hoarded by a Goddess. Using its pure white nature the raven lulled the goddess into a false sense of security and stole the items. The raven placed the sun in the day sky and the moon and stars at night. However he could find no place for the fire stick and as he searched over the land his feathers became black with soot and his voice became hoarse. Eventually he had to drop the burning stick and the fire merged with the land, explaining why certain stones when rubbed together create fire.
There are many other stories about ravens getting their colour. Some say that another bird coloured the raven in black with ash, and another says that he flew at night for too long and soaked up the colour. In these and many other fables the raven sacrificed its whiteness to help either the Gods, humanity or other animals flourish.
However some Native Americans consider the re-appearance of a white raven to be a portent of Armageddon3 and so perhaps we should join the philosophers and be less than happy to see these albino birds:
"At the end of the world there shall be seen a white Raven as a sign that the world is coming to an end, that will be the last of it."
On a personal note, the reason why I'm interested in albino birds is that before I was born when my mother was young she decided to do a school project on one of my grandfather’s hobbies; ornithology
My grandfather however was quite famous for making up nonsense stories to entertain children. For example if we went walking in the woods he would tell me that he knew how to gather milky ways from the secret milky way trees. Then after performing a slight-of-hand he seemingly plucked a chocolate bar from the branches.
Therefore when my mum produced a report on a rare albino blackbird which had nested in her garden, a few people thought that he was up to his old tricks. Certainly the school children thought it was funny that my mum had apparently been fooled by this tale of a white-blackbird.
However a school trip and a local newspaper article later my relatives' claims were vindicated and soon my grandmother’s kitchen was full of local twitchers trying to catch a glimpse of the extraordinary bird.
1 Picture of albino raven in the event that you think I’m talking malarkey
2 A collection of raven related legends
3 white raven as portent of doom
4In Icelandic the saying "sjalds_enir hvitir hrafnar" meaning an infrequent occurrence similar to our "once in a blue moon" literally translates as "white ravens are a rare sight"
An obsessive collection of raven facts quotes etc
this amazing article found by bookreader shows that white ravens exist and are alive today when not one but THREE were found in a churchyard in County Durham!
If anyone remembers the rhyme for ravens it goes: "One for bad news Two for mirth, Three is a wedding, Four is a birth." If the bride is superstitious then that’s the church to get married in!