In speculative theology, the science of the absolute person, or God, Boström gives a more detailed justification of the principle of his system. There, it is first of all maintained that independent reality necessarily must be spiritual (or, as we would say today, mental), and as such an independent consciousness or self-consciousness. This is the only thing that is simple. Since the complex presupposes the simple, self-consciousness must also be the ultimate principle of all reality. This self-consciousness — which Boström identifies with life—can thus not be conceived as attached to a substrate or a substance, but is precisely what is primary and original in everything.