This may be a misheard or miswritten version of non-affirmative art, referring to the Michael Foucault's Ceci n'est pas une pipe, a study of the painting of René Magritte. The title of Chapter 6 is “Peindre n’est pas affirmer”, which the English translation renders “Nonaffirmative Painting”.
. . .classical painting spoke – and spoke constantly – while constituting itself entirely outside language; hence the fact that it rested silently in a discursive space; hence the fact that it provided, beneath itself, a kind of common ground where it could restore the bonds of signs and the image.
Magritte knits verbal signs and plastic elements together, but without referring them to a prior isotopism. He skirts the base of affirmative discourse on which resemblance calmly reposes, and he brings pure similitudes and nonaffirmative verbal statements into play within the instability of a disoriented volume and an unmapped space. A process whose formulation is in some sense given by Ceci n’est pas une pipe.
A non-affirmative artist would be one who seeks to subvert the rationalizing categories of speech and employ his art to render, through paradox and self-reference, the inadequacy of those categories.