Philosophical Zombie

A philosophical zombie is a fictional entity that is identical to a human being, yet without conscious experience. This zombie might react exactly the same way a human would to actions that cause pain or pleasure, yet would have no internal experience of the emotion. 

This is impossible as only human beings have souls capable of processing subjective experiences, also known as qualia.

If we had no souls and were therefore purely physical beings, we would be able to create machines that can perfectly simulate us. If we do have souls, then no machine will ever experience qualia.