Negative causation occurs when an absence serves as cause, effect, or causal intermediary. Negative causation is genuine causation, or so I shall argue. It involves no physical connection between cause and effect. Thus causes need not be physically connected to their effects.

Sartre explains the theory of existential psychoanalysis in this treatise on human reality.

I IT is often declared or evidently assumed that causality is some kind of necessary connexion, or alternatively, that being caused is — non-trivially ...

The eclipse riddle -- Seeing surfaces -- The disappearing act -- Spinning shadows -- Berkeley's shadow -- Para-reflections -- Para-refractions : shadowgrams and the black drop -- Goethe's colored shadows -- Filtows -- Holes in the light -- Black and blue -- Seeing in black and white -- We see in the dark -- Hearing silence.

Can humans see causal interactions? Evidence on the visual perception of causal interactions, from Michotte to contemporary work, is best interpreted as showing that we can see some causal interactions in the same sense as that in which we can hear speech. Causal perception, like speech perception, is a form of categorical perception.