Limit and transgression depend on each other for whatever density of being they possess: a limit could not exist if it were absolutely uncrossable and, reciprocally, transgression would be pointless if it merely crossed a limit composed of illusions and shadows. But can the limit have a life of its own outside of the act that gloriously passes through it and negates it? For its part, does transgression not exhaust its nature when it crosses the limit, knowing no life beyond this point in time? Transgression, then, is not related to the limit as black to white, the prohibited to the lawful, the outside to the inside, or as the open area of a building to its enclosed spaces. Rather their relation takes the form of a spiral which no simple infraction can exhaust. Perhaps it is like a flash of lightning in the night, which, from the beginning of time, gives a dense and black intensity to the night it denies, which lights up the night from the inside, from top to bottom, and yet to the dark the stark clarity of its manifestation, its harrowing and poised singularity .
Michel Foucault: Preface to Transgression
An interesting interpretation by Steve Weston can be found here.