I’ve just been thinking about psionics in AD&D and in particular how you could run a Dark Sun campaign without having to bother with the psionic rules and instead use something like 3rd edition sorcerers with limited spell lists.
And I think I know see why psionics always seemed redundant, as someone starting with 3rd edition. In AD&D, magic is something that is always learned. All you need is to meet the ability score requirements and you can learn arcane and divine magic. There was no such thing as being born with magic power or having a special natural talent that opens the path for magic training to you.
And that was the point of psionics. Psionics is a type of magic that can not be taught, but is something you are born with. A psion was simply a person who spend all his training on improving and expanding the powers he was born with, at the cost of forgoing the training of any other skills other character classes get.
And that’s exactly the same thing that sorcerers do. 3rd edition said that characters do have the option of being born with magic powers. But instead of bothering with an alternative list of abilities and mechanics, sorcerers simply use the same spells that wizards do.
But when they later added psionics to the game, that created a redundancy. Sorcerers and psions have the same fluff. They fill the same role only with different mechanics.
And that’s why you sometimes see people making such a big deal about psionics being not magic and being completely different because the power comes from within. In 3rd edition, that’s the same thing as sorcerers, but in AD&D, it was indeed a big difference. Magic was always something you learned about altering the world around you, never something you had naturally within you.
It also explains why the 3rd edition Monster Manual has creatures with psionics, which work 100% like spell-like abilities. In AD&D, aboleths and yuan-ti were getting their powers from the list of psion powers, not from the spell-lists of wizards and clerics.Apparently some writer wanted to keep calling it psionics, even though they were now spell-like abilities in everything but name.
So now I think that when you use psionics in a 3rd edition or Pathfinder game, that campaign should not include sorcerers. Other classes like bards or beguilers can stay, their spells seem to have always been considered learned instead of inborn (except for dragon disciples, but those are their own can of worms.)