Full Idea
The essential principle of phenomenology is that 'all consciousness is consciousness of something'.
Gist of Idea
Phenomenology assumes that all consciousness is of something
Source
Jean-Paul Sartre (Transcendence of the Ego [1937], I (B))
Book Reference
Sartre,Jean-Paul: 'The Transcendence of the Ego' [Routledge 2004], p.10
A Reaction
This idea is found well before Husserl, in Schopenhauer (Idea 4166). It seems to contradict a thought such as Locke's (Idea 1202), that self-awareness is a separate and distinct criterion for personal identity. Sartre gives a nice account.
Related Ideas
Idea 4166 A consciousness without an object is no consciousness [Schopenhauer]
Idea 1202 A person is intelligent, rational, self-aware, continuous, conscious [Locke]