Full Idea
The in-itself has to express itself outwardly and become for itself, and this means simply that it has to posit self-consciousness as one with itself.
Gist of Idea
The in-itself must become for-itself, which requires self-consciousness
Source
Georg W.F.Hegel (Phenomenology of Spirit [1807], Pref 26)
Book Reference
Hegel,Georg W.F.: 'Phenomenology of Spirit', ed/tr. Miller,A.V. /Findlay,J.N. [OUP 1977], p.15
A Reaction
This famous distinction seems to be at the core of idealism, but also to be the germ of existentialism (prior to Kierkegaard), which builds on this view of what it means to exist as an individual. Self-consciousness in nature is inevitable?