Memento mori should be read: don't forget to die. — Slavoj Žižek

'Father, why is the sky blue?' - the child is not really interested in the sky as such; the real stake of the question is to expose father's impotence, his helplessness in the face of the hard fact, to present the whole chain of reasons leading to it. The blue of the sky thus becomes not only the father's problem, but in a way even his fault. The sky is blue, and you're just staring at it like an idiot incapable of doing anything about it!

Subject - (1) a person subject to political rule; (2) a free agent, instigator of its activity - subjects can realize themselves as free agents only by means of redoubling themselves as, only in so far as they project, transpose the pure form of their freedom into the very heart of the substance opposed to them; into the person of the subject-monarch as head of state.

The famous MacGuffin , the Hitchockian object, the pure pretext whose sole role is to set the story in motion but which is in itself nothing at all - the only significance of the MacGuffin lies in the fact that it has some significance for the characters - that it must seem to be of vital importance to them... - that's a MacGuffin, a pure nothing which is non the less efficient... what Lacan calls object petit a: a pure void which functions as the object cause of desire.