One of your friends argues that he has read in previous chapters that there can be no electric field inside a conductor. And hence there can be no current through it. What is the fallacy in this argument?
The fallacy in the argument of the friend is that in the previous chapters the focus was on stationary charges and not moving charges and hence with no moving charges there will be no electric field inside a conductor and hence no current. However, in case of moving charges or current there will be an electric field due to the applied potential difference.