This classic essay is part of the Falsification Symposium, so in order to understand it you will need to have read the previous Anthology extract by Flew & Hare. Basil Mitchell is replying to Antony Flew's claim that religious language is meaningless because believers will not allow their statements to be falsified. Antony Flew then replies, offering a criticism of Mitchell's position and that of R.M. Hare from the previous extract.
This extract can be divided into two sections:
if there is nothing which a putative assertion denies then there is nothing which it asserts either; and so it is not really an assertion - Antony Flew