Contradiction could be seen as an antagonistic violation of the law of identity While the law of identity states that $A = A$, i.e. a thing is always equal to itself, contradiction could mean a violation of the law of identity such that $A = A \land A \neq A$.

For Hegeland possibly Marx a contradiction is a key component of dialectic such that two contradictory ideas or forces sublate one another and are resolved into a new idea, such as the contradiction between being and nothingness, which is resolved in the idea of "becoming."

For Hegel a contradiction was merely the product of reason