Simulacra -
The dream world hides a lack of reality, as is shown when Cobb first takes Ariadne into a dream, as she has a conversation with Cobb without realising they appeared at the cafe or how they got there.

Architects -
Postmodernism's foundation is the idea that everyone has their own idea of what reality is, and Inception's Architects are the physical form of this, as they can bend reality, changing what they want as long as the individual's subconscious can recognise it as being part of their own reality.

Fragmentary Story -
For the most part, the story follows a direct (although confusing) path apart from a small number of exception, namely the beginning and end. In the beginning of the film, Cobb infiltrates Saito's dream in order to get a safe code, waking up on shore and being dragged to Saito's table; while at the end of the film, Cobb is shown waking up on the same beach and being dragged to the table in the same way, with Saito looking old and 'full of regret', much like in the beginning of the film, with the only difference being a change of circumstances.

Time -
Time plays a major role in Inception as each layer deeper you go within a dream, time in the real world is slower, so five minutes in the real world equalled about 40 minutes in the first dream layer when Cobb was teaching Ariadne. This is explained as the subconscious is able to think faster than time goes by in the real world, although that is a hard claim to make as time is relative to an individual's perception, as someone who is having an enjoyable time watching a film might feel as though 2 hours has gone by quickly, someone else who dislikes it might believe that it felt like significantly longer than only 2 hours.

Ending -
When Cobb wakes up in the plane after escaping Limbo and arrives back home to see his children, the viewer is left wondering whether what is being shown on-screen is reality or just another dream, as the spinning top is never outright shown stopping. But, this also causes the viewer to ask 'what is the difference between a dream and reality?' as your world is filled with your own perceptions that define your interpretation of what reality really is.