Couldn't this argumentation be used as a reason why warlocks, sorcerers, and bards are not necessary when wizards already have most of their spells? And FYI in at least 3e and 4e it was called their "power list."
Of course! And that's why all four fall into the "arcane" power source. Because they all have a larger amount of overlap. Those 3 could quite easily be made Wizard subclasses with applicable backgrounds. I'm won't argue that they shouldn't be classes though, because its already too late-- they are classes, so nothing any of us can say can change that.
Yes, there is overlap. And indeed, the three sources share several of the same spells. But if we were to mention off the tops of our heads the first five spells we think of that would be for the Cleric, Druid, and Wizard... I don't think any of them would be the same. We could probably go to 10 defining spells for those three classes and almost if not all would be different.There is overlap between primal and arcane, particularly with things like elemental magic. There is overlap between divine and primal sources, particularly with things like healing and restorative magic.
I don't think the same could be said for the Psion. Mention the first 10 "spells" a Psion would have as defining abilities and almost every single one is something the Wizard already does.
I think that we could say - much as Pathfinder 2 does with its "Occult" power source - that overlap can exist between divine (and ki) and arcane sources that are suitable for psionic magic: mental magic, divination, telekinesis, monk-like mysticism, psycho-metabolism, mind over body, astral dimension and constructs, etc.
If there was just merely some overlap, I'd agree with you. But the question is actually where is there NO overlap between the Psion and the Wizard? Is there any defining ability the Psion can hang its hat on that the Wizard doesn't also do? THAT'S the issue I think. If we can't come up with a single thing (let alone five or more) that Psions would do that the other power sources don't do... then that's a pretty good indication that a Psion would only be a different thing in name only.
In many ways this is true, but again... the Warlock and the Sorcerer are both arcane classes and thus some overlap with the Wizard can be expected, plus they already ARE classes, so no amount of complaining can get them removed. The same cannot be said of the Psion.shrug That seems less like a real issue and more like the flimsy excuse that people are making to keep the psion from consideration as a class. It doesn't really hold up much weight under scrutiny really. The sorcerer and warlock both have smaller spell lists than the wizard and do similar things.
So if the Warlock and Sorcerer's abilities overlap with the Wizard, does that then mean the Psion should also be an arcane class too since they almost entirely overlap? What would the reaction be if the Psion was made an arcane class (since it overlaps so much?) I suspect people would freak. They SAY there is a marked difference between the Wizard and the Psion... that one is magic and one isn't... but what truly is the difference other than a couple fluff ribbon abilities? No spellbook, no components. What else IS there that makes the Psion truly separate and different from any of the arcane classes? I honestly can't think of any. And if we can't get that list of at least 5 things that the Psion does that no other classes can... asking if its truly necessary is not out of line.