One living equates to one dream citizen. This has always been the unwavering rule of this world.
And ever since Doug forcibly connected his existence to Philip, there was no way out of this arrangement. Their fates were inexorably and permanently intertwined.
This so-called 'connection' requires careful planning, especially for mentalists, who had to carefully select their counterpart dream citizen.
Dream citizens were also different and not created equal. Some were strong, while others were weak.
And... If a mentalist chooses the weak one, his ability will be greatly discounted in the future!
Philip had learned from other dream citizens that higher-level mentalists were required to create a city-like structure in their consciousness space. The connected dream citizen would oversee this city when the mentalist was absent or occupied in the real world.