Any contradiction or paradox.
In the thought of the German philosopher Immanuel Kant (1724–1804): an apparent contradiction between valid conclusions; a paradox.
Competition by parts of a system or its users for a limited resource.
Argument, contest, debate, strife, struggle.
A point maintained in an argument, or a line of argument taken in its support; the subject matter of discussion of strife; a position taken or contended for.