Applicable to different approaches in critical theory.
For Theory:
Politics is pervasive
language is constitutive
Truth is provisional
meaning is contingent and
Human nature is a myth
Many of the notions which we would usually regard as the basic 'givens' of our existence (including our gender identity, our individual selfhood, and the notion of literature itself) are actually fluid and unstable things, rather than fixed and reliable essence. Instead of being solidly 'there in the real world of fact and experience, they are socially constructed, that is, dependent on social and political forces and on shifting ways of seeing and thinking. Hence, no overarching fixed truths' can ever be established. The results of all forms of intellectual enquiry are provisional only.
Every practical procedure (for instance literary criticism) presupposes a theoretical perspective of some kind. To deny this is to place our own theoretical position beyond scrutiny as something which is 'common sense' or 'simply given'. The problem with this view is that it tends to discredit one's own project along with all the rest, introducing a 'relativism' which disables argument and cuts the ground from under any kind of commitment.
Language itself conditions, limits, and predetermines what we see. Thus all reality is constructed through language, so that nothing is simply 'there' in an unproblematical way-everything is a linguistic/textual construct. In literature as in all writing, there is never the possibility establishing fixed and definite meanings: rather, it is characteristic of language to generate infinite webs of meaning so that all texts are necessarily self contradictory, as the process of deconstructions will reveal.
There is no final court of appeal court of appeal in there matters, since literary texts, once they exist, are viewed by the theorist as independent linguistic structures whose authors are always 'dead' or 'absent'.