A type of paradox consisting of a contradiction between two apparently unassailable propositions. antinomic adj. [From Greek anti against + nomos a law]
Kant's antinomies (paradox): when something is both necessary and impossible: for Kant, when regulative principles are taken outside their proper sphere of employment, as they are when theorizing about the world as a whole, contradiction results.
The solution to this conflict of reason with itself is that the principles of reasoning used are not ‘constitutive’, showing us how the world is, but ‘regulative’, or embodying injunctions about how we are to think of it.