Opinions are theories, concepts can never have presence.

Derrida - identity formation deformation presence and absence

The dialectic of absence and presence, or an exposure of the importance of the dialectic of absence and presence is fundamental to the process of destabilising formation into deformation. 

The process of formation is at the same time, inevitably, a process of deformation. Presence is constituted by its drawing on absence For Derrida, it is the trace of the ‘other’, absence, which signs in the sign called presence in our speech or writing. 

It follows, concepts can never establish a full and replete presence for themselves. This, as Derrida says, undermines Western metaphysics because it is a claim to full presence which underpins metaphysical concepts and procedures.