Quote from : Literary Theory: An Introduction Book

Derrida… labels as ‘metaphysical’ any such thought system which depends on an unassailable foundation, a first principle or unimpeachable ground upon which a whole hierarchy of meanings may be constructed. It is not that he believes that we can merely rid ourselves of the urge to forge such first principles, for such an impulse is deeply embedded in our history, and cannot — at least as yet — be eradicated or ignored. Derrida would see his own work as inescapably ‘contaminated’ by such metaphysical thought, much as he strives to give it the slip. But if you examine such first principles closely, you can see that they may always be ‘deconstructed’: they can be shown to be products of a particular system of meaning, rather than what props it up from the outside.