But that's the issue. Why would Zerg have purity of essence? What the fuck does essence even refer to in this context? And why do Protoss have purity of form? What is form?
According to the SC1 manual, about which I care because it added a lot of depth to the story, purity of form and purity of essence were two philosophical concepts invented by the Xel'Naga to analyse their failure with the Protoss. The Protoss were the most promising race the Xel'Naga had worked on, and thy decided that the Protoss' "essence" had been corrupted by their ego, their pride. The Xel'Naga were especially shocked when the Protoss attempted to "disconnect" themselves from the Khala. So they decided they would follow a completely different course with the Zerg, not caring about the purity of the "form" (body) and instead about the purity of "essence". What that means is that the Zerg can take almost any form, alter themselves out of recognition, switch strands of DNA among the various strains, but they would still be Zerg because they were bound to the Overmind and the collective sentience.
The Protoss have purity of form (they all share the physical traits) and the Zerg don't. The Zerg have purity of essence due to the hive mind. It is unclear whether or not the Xel'Naga would consider the Khalai Protoss to have purity of essence. My guess is no, since they are still individuals.
So when the Zerg collect DNA strands, they are collecting form, not essence. I guess "form" didn't sound alien enough for the writers... By SC1 manual standards, the Terran technically have purity of form but not purity of essence, and the so-called primal Zerg have neither.
Note that the Xel'Naga did not consider purity of form as a perfection to be achieved, but as a distraction from what they really wanted to create (purity of essence).
According to the SC1 manual, about which I care because it added a lot of depth to the story, purity of form and purity of essence were two philosophical concepts invented by the Xel'Naga to analyse their failure with the Protoss. The Protoss were the most promising race the Xel'Naga had worked on, and thy decided that the Protoss' "essence" had been corrupted by their ego, their pride. The Xel'Naga were especially shocked when the Protoss attempted to "disconnect" themselves from the Khala. So they decided they would follow a completely different course with the Zerg, not caring about the purity of the "form" (body) and instead about the purity of "essence". What that means is that the Zerg can take almost any form, alter themselves out of recognition, switch strands of DNA among the various strains, but they would still be Zerg because they were bound to the Overmind and the collective sentience.
The Protoss have purity of form (they all share the physical traits) and the Zerg don't. The Zerg have purity of essence due to the hive mind. It is unclear whether or not the Xel'Naga would consider the Khalai Protoss to have purity of essence. My guess is no, since they are still individuals.
So when the Zerg collect DNA strands, they are collecting form, not essence. I guess "form" didn't sound alien enough for the writers... By SC1 manual standards, the Terran technically have purity of form but not purity of essence, and the so-called primal Zerg have neither.
Note that the Xel'Naga did not consider purity of form as a perfection to be achieved, but as a distraction from what they really wanted to create (purity of essence).