||A deductive inference transmits warrant just in case, roughly put, one can earn a warrant for the conclusion by deploying one's warrant for the premise and performing the deduction. If one cannot earn a warrant for the conclusion in this way, then the inference is said to be an instance of 'transmission failure'. Transmission failure is an idea that divides epistemologists. Some have insisted that any deductive inference will transmit warrant. And, even amongst those who accept that there are genuine cases of transmission failure, there is relatively little agreement as to which the offending inferences are and what is responsible for the phenomenon. The issue takes on an additional philosophical significance due to the fact that some of the disputed inferences are themselves philosophically significant - such as McKinsey's paradox for externalist theories of content and Moore's notorious 'proof' of the existence of the external world.