The goal of Georg Friedrich Wilhelm Hegel's Phenomenology of Spirit is to convince its reader that he is not merely himself but Absolute Spirit or Universal Reason as well. The functionality of reason and the positing of ethical rules by individuals in Hegel's conception of history brings history to a point where some individual finally recognizes that the process of such positing is Universal, non individual dependent. Hence its own being that encompasses every human being, despite involving the activities of a multitude of human beings.

How does Hegel turn the human process of reasoning into an independent self-aware being? He proves its independent existence by showing that it satisfies the three criterions of what constitutes independent existence

Hegel's criteria of personhood is based on three things - consciousness of self, consciousness of object other than self, and consciousness of representation of object that is non-self by self. Universal reason becomes an individual being because it satisfies all three concepts.

An individual at a certain point history, namely Hegel himself, realizes that reason is a process that isn't limited to any individual human being but reveals itself as a constant throughout time. In this case, reason realizes its own independent existence and achieves self-consciousness.

A critic of Hegel would of course say that this is rather the case of an individual philosopher merely positing universal reason, and on dubious grounds, namely by illegally turning a process of reasoning into a subject. But this is merely an aside; let's look at how Hegel uses his two criterions of selfhood to prove reason's existence as an independent being.

Universal reason, of course, satifies the other conditions of selfhood - being aware that there are objects other than itself, namely the humans that use reason but are merely agents that do not comprise the identity of the universal reason itself. (They take part in this process/being but it is independent of them and they are others to it, albeit others that it uses to set itself into function.) The other object that is a non-self that reason is aware of is nature. According to Hegel, nature lives outside of the mathematical and scientific order that reason tries to impose on it because it is chaotic and confounds all attempts to completely classify and order it.

And here were come to the satisfaction of the third criterion of selfhood - the awareness of the self that it creates ]representations] of the non self. The laws of nature, scientific and mathematical, are understood by reason as its own attempts to represent the workings of nature. Reason knows nature to have its own life that does not conform to its representations. Hence, reason realizes that these rules that it sees in nature are only representations subjectively imposed by it rather than existing objectively in nature itself.

Source: Forster, Michael. Hegel's Idea of a Phenomenology of Spirit. University of Chicago Press: Chicago and London, 1998.
Notes: Refer to Johann Gottlieb Fichte's philosophy to learn more about the origins of the criterion of selfhood.