phenomena are ontologically primitive relations—relations without preexisting relata. The notion of intra-action (in contrast to the usual “interaction,” which presumes the prior existence of independent entities/relata) represents a profound conceptual shift. It is through specific agential intra-actions that the boundaries and properties of the “components” of phenomena become determinate and that particular embodied concepts become meaningful. A specific intra-action (involving a specific material configuration of the “apparatus of observation”) enacts an agential cut (in contrast to the Cartesian cut — an inherent distinction—between subject and object) effecting a separation between “subject” and “object.” That is, the agential cut enacts a local resolution within the phenomenon of the inherent ontological indeterminacy.
(Barad, Posthumanist Performativity: Toward an Understanding of How Matter Comes to Matter (2003))