Back when the planetary orbits were documented for prediction purposes, Mercury was noted to have some obvious deviations from its predicted path. Several astronomers theorized these perturbations could be caused by another planet, orbiting closer to the Sun. The theoretical planet was named Vulcan, and its potential properties were described. A few astrologers leaped upon this theoretical planet and included it in their charting. For all I know, some may still include it as woo doesn't die off easily. Years later, Einstein's theory of relativity explained the orbital oddities sufficiently, no extra planet is necessary. Now, put yourself in the place of an astrologer who had grown up believing in Vulcan. You had cast hundreds, maybe thousands of charts including this object. How do you think you would react to having someone take this object away from you? Now carry that to today. Do you incorporate Pluto in your astrological charting?
There's a big difference in these two examples, Vulcan was found not to exist, and Pluto very much still exists, but was demoted by a bunch of astronomers because it didn't meet certain specifications.
In order to understand what goes on in the mind of astrologers when planets are discovered (or not), we have to look at the theory of spiritual astrology. I think I mentioned this earlier on, but basically, according to this theory, planets are discovered by astronomers when they are
meant to be discovered. The theory says that when planets are discovered, there is something going on in human evolution that represents the meaning of that planet.
One fact that always amazes me is how the outer planets Uranus, Neptune and Pluto got their names. These planets were named after Greek or Roman gods, which
by coincidence , happen to have the same sort of psychological traits that astrologers see in people with these planets in strong aspect to the inner planets in their horoscopes.
I know what you are going to say! You are going to say that astrologers just see what they want to see, and cherry pick charts which only exhibit traits that prove their theory, but, what can I say, I didin't make the theory up. The biggest evidence that this might be true is to look at the important events in history from around 1781, 1846 and 1930, which I wrote about on page 2 or 3 so won't repeat.
When we look at Pluto in relation to history, and at thousands of horoscopes with it, we can correlate it to certain traits - even with all the possible errors that skeptics have pointed out, you would, I think, have a hard time convincing astrologers that Pluto didn't have a very strong psychological correlation in a chart. Pluto says a lot to astrologers about power, control secrecy, and transformation, and it would be difficult to analyze a person's horoscope without it. Just because Pluto's external classification has changed from planet to dwarf planet doesn't change its spiritual and psychological symbolism at all.
The recent declassification did bring other changes as well. The object Ceres, which was previously classed as an asteroid, has now been upgraded to a dwarf planet. This hasn't affected many astrologers, as they still think that Sun through Pluto works for them, but others think that Ceres evens out the male-female balance a little.
Back in the 1850s when Vulcan was proposed, astrologers were still waiting for a body to be discovered which would explain certain human personality traits, and also divine characteristics. In many ways, Vulcan's symbology was similar to Pluto's, and we can't blame astrologers for doing what they do just because science was doing science (making a theory, proving it wrong and then trying again). In the tarot series (drawn up around 1200 to correspond to the letters of the Hebrew alphabet), and in the kaballistic Tree of Life, the key/path known as Key 20, or Judgement, was assigned to this "new" planet, first Vulcan, and then Pluto.