I've found the discussion of Saturn and Pluto which has emerged between Sandstone and MaeMae intriguing - largely because I've always found it difficult to draw a sharp distinction between these planets. I have Pluto on the IC ruling my Moon in Scorpio, and Saturn exactly sesquiquadrate my Sun/Moon midpoint.
(If you allow two degrees and twenty minutes I have a sesquiquadrate between them, and they both aspect my Mercury in Aquarius (Saturn) in the 8th (Pluto) well within orb. There are other things like Venus in Capricorn exactly septile Pluto and trine Saturn, and Sun in Aquarius in the 8th exactly binovile Saturn and quincunx Pluto. Don't know if these aspects are relevant to this though).
I have always associated both of these planets with death, and they are both personified in various mythologies as 'lord of the dead'. What MaeMae says about Saturn only being interested in what is right in front of it is surely relevant. If Saturn symbolises the self-circumscribing nature of individual consciousness, then we can only experience the planets beyond Saturn through Saturn's filter, unless we are having some kind of break-down or superconscious experience.
They both clearly share an urge towards self-determination which is quite unlike the needs for autonomy of other planets like Sun, Mars, Uranus.
If Saturn is the boundary where personal meets collective, and Pluto is the collective survival instinct which by necessity must destroy much of that which individuals have made of themselves and the world (Saturn), then the dynamic between Saturn and Pluto could be seen as backbone of evolution on every level of existence.
When Chronos (Saturn) was overthrown by Zeus and Hades and the gang, and Chronos was banished to Tartaros beneath the ground, Hades (Pluto) also chose to live beneath the ground. That was (pretty much) the last anyone ever saw of either of them. Perhaps this in some way symbolises that in all manifest things, Saturn and Pluto are always present in a way that the other archetypes aren't. There could be no transformation with out form, and a form can only be defined by what else it was, might have been, or might become.
I'm not sure exactly where I'm going with this, so I'll leave it there for now.
I also thought this Dane Rudhyar quote worth sharing:
"In its highest form [Pluto] refers to the greatest contribution an individual person can make to his society or to humanity in general. But before he can make such an effectual and significant contribution, the individual must pass through experiences of at least relative psychological denudation and soul emptiness."
From THE PLANETARY ALPHABET
http://www.khaldea.com/rudhyar/astroarticles/planetaryalphabet.php